user-1: I mused that clearly, certain efforts are necessary for the path. But, I can easily imagine a person exerting lots of efforts towards a detrimental goal, or a person exerting a bit of effort towards a wholesome goal. So, effort in itself seems not directly related to good qualities. 
Another example is a proficient meditator for whom meditation might be easier, but more potent and pleasant; this contrasts with the beginner who struggles and must apply effort. The experienced meditator might generate more effect with less effort.
What is the relationship in Buddhism of effort to its resulting benefit? Is it indirect?
Thank you 

user2282: 
Another example is a proficient meditator for whom meditation might be easier, but more potent and pleasant; this contrasts with the beginner who struggles and must apply effort. The experienced meditator might generate more effect with less effort.

There're many other examples we see in our daily life. Weren't you surprised and maybe even a little bit envious of that super genius friend of yours back in 4th grade who aced all the math exams without spending much time doing his homework assignments, while you only got a passing grade even after working your behind off on those homework exercises? How about that music kid in 6th grade who breezed thru Mozart's Concerto No.21 while you still struggled with your Yankee Doodle! So the key point is, unless you believe in complete sheer chance, a completely random rolling of the genetic dice, Or succumb to the idea of a God who, in his own mysterious way, made those friends of yours way smarter or way more talented, then you will have to question where all those potentials came from? If they weren't by chance, by some mysterious force, or came out of thin air, then there always exists the possibility that your math/piano buddies had already worked their behinds off at some point in their previous lives, while you, back then only spent most of your days fooling around, right? So bottom line is, think of efforts like the law of conservation of energy, as long as one invests in it in a good wholesome way, it won't be a wasteful investment.

user-1: One aspect of effort translates from the pali concept viriya. It is included in 

the ten perfections (dasa pāramiyo) 
the seven factors of awakening (satta bojjhaṅgā)
the five strengths (pañcabalāni)
the five spiritual faculties (pañc' indriyāni)

Just as you concluded yourself, viriya is bundled with the other perfections/factors since it isn't enough on it's own. 
For instance, it is not a coincidence that equanimity (upekkha) appears alongside effort/viriya. Effort on it's own runs the risk of becoming unwholesome craving (tanha), and is more wholesome when tempered by the other wholesome factors mentioned above, especially equanimity. This is elaborated on in Visuddhimagga:

if the vigor faculty is too strong, the faith faculty cannot perform its function of convincing, nor can the rest of the faculties perform their several functions. So in that case the excessive strength of the vigor faculty should be reduced by cultivating (the enlightenment factors of) tranquillity, concentration and equanimity.


user295: Any action which requires more effort or planning requires more volitional thoughts. This compounds the karmic effort. E.g. killing a mosquito is quite reactive and requires little thought relative to going hunting for larger game. Therefore, killing a mosquito has fewer consequences. Similarly for meritorious deeds.
In meditation, when one is struggling this is either lack of concentration, mindfulness or defilements surfacing. An experienced mediator may experience only lesser about of such negative states and more positive states. Therefore, a more experienced meditator may accumulate more merit in the course of meditation.
Ultimately what matters is the times one generate wholesome/unwholesome volitional activities when taking action.
With regard to right-effort, one must put effort into the Four Right Exertions. More the effort more the merit. But one should aware that this effort is not excessive, in which case will make you stressed. 

user471: From MN 117, we read that Right Effort (samma vayamo) must go in the right direction:

"One tries to abandon wrong view & to enter into right view: This is
  one's right effort...
"One tries to abandon wrong resolve & to enter into right resolve:
  This is one's right effort...
"One tries to abandon wrong speech & to enter into right speech: This
  is one's right effort...
"One tries to abandon wrong action & to enter into right action: This
  is one's right effort...
"One tries to abandon wrong livelihood & to enter into right
  livelihood: This is one's right effort."

Not just the right direction, but also the right amount of effort - not too much and not too little.
From AN 6.55 (a vina is an indian stringed musical instrument):

"And what do you think: when the strings of your vina were too taut,
  was your vina in tune & playable?"
"No, lord."
"And what do you think: when the strings of your vina were too loose,
  was your vina in tune & playable?"
"No, lord."
"And what do you think: when the strings of your vina were neither too
  taut nor too loose, but tuned to be right on pitch, was your vina in
  tune & playable?"
"Yes, lord."
"In the same way, Sona, over-aroused persistence leads to
  restlessness, overly slack persistence leads to laziness. Thus you
  should determine the right pitch for your persistence, attune the
  pitch of the [five] faculties [to that], and there pick up your
  theme."


-1: <p>I mused that clearly, certain efforts are necessary for the path. But, I can easily imagine a person exerting lots of efforts towards a detrimental goal, or a person exerting a bit of effort towards a <em>wholesome</em> goal. So, effort <em>in itself</em> seems not directly related to good qualities. </p>

<p>Another example is a proficient meditator for whom meditation might be easier, but more potent and pleasant; this contrasts with the beginner who struggles and must apply effort. The experienced meditator might generate more effect with less effort.</p>

<p><strong>What is the relationship in Buddhism of effort to its resulting benefit? Is it indirect?</strong></p>

<p>Thank you </p>
 2282: <blockquote>
  <p>Another example is a proficient meditator for whom meditation might be easier, but more potent and pleasant; this contrasts with the beginner who struggles and must apply effort. The experienced meditator might generate more effect with less effort.</p>
</blockquote>

<p>There're many other examples we see in our daily life. Weren't you surprised and maybe even a little bit envious of that super genius friend of yours back in 4th grade who aced all the math exams without spending much time doing his homework assignments, while you only got a passing grade even after working your behind off on those homework exercises? How about that music kid in 6th grade who breezed thru Mozart's Concerto No.21 while you still struggled with your Yankee Doodle! So the key point is, unless you believe in complete sheer chance, a completely random rolling of the genetic dice, Or succumb to the idea of a God who, in his own mysterious way, made those friends of yours way smarter or way more talented, then you will have to question where all those potentials came from? If they weren't by chance, by some mysterious force, or came out of thin air, then there always exists the possibility that your math/piano buddies had already worked their behinds off at some point in their previous lives, while you, back then only spent most of your days fooling around, right? So bottom line is, think of efforts like the <a href="https://en.wikipedia.org/wiki/Conservation_of_energy" rel="nofollow noreferrer">law of conservation of energy</a>, as long as one invests in it in a good wholesome way, it won't be a wasteful investment.</p>
 -1: <p>One aspect of effort translates from the pali concept viriya. It is included in </p>

<ul>
<li>the ten perfections (dasa pāramiyo) </li>
<li>the seven factors of awakening (satta bojjhaṅgā)</li>
<li>the five strengths (pañcabalāni)</li>
<li>the five spiritual faculties (pañc' indriyāni)</li>
</ul>

<p>Just as you concluded yourself, viriya is bundled with the other perfections/factors since it isn't enough on it's own. </p>

<p>For instance, it is not a coincidence that equanimity (upekkha) appears alongside effort/viriya. Effort on it's own runs the risk of becoming unwholesome craving (tanha), and is more wholesome when tempered by the other wholesome factors mentioned above, especially equanimity. This is elaborated on in Visuddhimagga:</p>

<blockquote>
  <p>if the vigor faculty is too strong, the faith faculty cannot perform its function of convincing, nor can the rest of the faculties perform their several functions. So in that case the excessive strength of the vigor faculty should be reduced by cultivating (the enlightenment factors of) tranquillity, concentration and equanimity.</p>
</blockquote>
 295: <p>Any action which requires more effort or planning requires more volitional thoughts. This compounds the karmic effort. E.g. killing a mosquito is quite reactive and requires little thought relative to going hunting for larger game. Therefore, killing a mosquito has fewer consequences. Similarly for meritorious deeds.</p>

<p>In meditation, when one is struggling this is either lack of concentration, mindfulness or defilements surfacing. An experienced mediator may experience only lesser about of such negative states and more positive states. Therefore, a more experienced meditator may accumulate more merit in the course of meditation.</p>

<p>Ultimately what matters is the times one generate wholesome/unwholesome volitional activities when taking action.</p>

<p>With regard to right-effort, one must put effort into the <a href="https://en.wikipedia.org/wiki/Four_Right_Exertions" rel="nofollow noreferrer">Four Right Exertions</a>. More the effort more the merit. But one should aware that this effort is not excessive, in which case will make you stressed. </p>
 471: <p>From <a href="https://www.accesstoinsight.org/tipitaka/mn/mn.117.than.html" rel="nofollow noreferrer">MN 117</a>, we read that <a href="https://www.accesstoinsight.org/ptf/dhamma/sacca/sacca4/samma-vayamo/index.html" rel="nofollow noreferrer">Right Effort (<em>samma vayamo</em>)</a> must go in the right direction:</p>

<blockquote>
  <p>"One tries to abandon wrong view &amp; to enter into right view: This is
  one's right effort...</p>
  
  <p>"One tries to abandon wrong resolve &amp; to enter into right resolve:
  This is one's right effort...</p>
  
  <p>"One tries to abandon wrong speech &amp; to enter into right speech: This
  is one's right effort...</p>
  
  <p>"One tries to abandon wrong action &amp; to enter into right action: This
  is one's right effort...</p>
  
  <p>"One tries to abandon wrong livelihood &amp; to enter into right
  livelihood: This is one's right effort."</p>
</blockquote>

<p>Not just the right direction, but also the right amount of effort - not too much and not too little.</p>

<p>From <a href="https://www.accesstoinsight.org/tipitaka/an/an06/an06.055.than.html" rel="nofollow noreferrer">AN 6.55</a> (a <a href="https://en.wikipedia.org/wiki/Veena" rel="nofollow noreferrer">vina</a> is an indian stringed musical instrument):</p>

<blockquote>
  <p>"And what do you think: when the strings of your vina were too taut,
  was your vina in tune &amp; playable?"</p>
  
  <p>"No, lord."</p>
  
  <p>"And what do you think: when the strings of your vina were too loose,
  was your vina in tune &amp; playable?"</p>
  
  <p>"No, lord."</p>
  
  <p>"And what do you think: when the strings of your vina were neither too
  taut nor too loose, but tuned to be right on pitch, was your vina in
  tune &amp; playable?"</p>
  
  <p>"Yes, lord."</p>
  
  <p>"In the same way, Sona, over-aroused persistence leads to
  restlessness, overly slack persistence leads to laziness. Thus you
  should determine the right pitch for your persistence, attune the
  pitch of the [five] faculties [to that], and there pick up your
  theme."</p>
</blockquote>
