Q:

Which is more appropriate , "was" or "were" and why?

If I were you and was ...

Or,

If I were you and were...

Google results show that the former is correct but hypothetical statements use "were". I'm confused between the two sentences.

A:

Do you mean a sentence like, "If I were you and [was/were] planning this party..."?
"Were" is the technically correct option in this case, for the reason you described. There are two hypotheticals: if I were in your place, and if I were planning the party. The same rules apply to both.
That said, this particular rule often gets ignored in casual speech, and you might hear it both ways.

