you should always workout with free weight , as they allow you to use the natural free-range of motion , stabilizer muscle , and proper posture . there be absolutely no reason you should work out on machine unless you be a complete beginner or injure . machine be great for safety , but not much else . if you be go to invest in a dumbbell set , get the one that go to 50 pound at the minimum . everything else be just a waste . you will outgrow you old weight as you constantly and consistently work out . if dumbbell set be too expensive for you , then consider join a gym for $ 20 a month or get 3 dumbbell weight -lrb- 10 pound , 25 pound , and 50 pound -rrb- . there be no need to even invest in a dumbbell set until you bodyweight exercise and stability exercise become too easy -lrb- over 100 push-up , 20 pull-up , and 6 minute mile -rrb- . until then , use you body weight ! it be cheaper , faster , and easier . if you do not feel the burn after 10 repetition , you be do the exercise wrong . in all exercise , it be the eccentric portion of the exercise that build muscle . do the exercise in a smooth , controlled fashion with a 3 concentric and 6 eccentric count . squeeze at the peak of the motion to get that extra pump . as in all exercise , make sure to keep you wrist straight and check you posture with these seven vital point : foot hips-width apart and point straight ahead ; knee slightly bent ; pelvis at perfect middle , as if you be sit at a bar stool ; stomach tight , but not flex ; chest straight and align on top of rib ; shoulder parallel to rib ; and neck straight on top of body