The goal with the weight increases is gradual progressive load across the board, not just one exercise. I'd use 5 lb weighs to increase compounds and 2.5 lb weights for iso stuff. You will not ALWAYS progress up in weight every week. Progress gets harder as you train.
Ex. If you are doing a particular compound to failure @ 8 reps, wait until you can hit 10+ reps and then up it. The 10 more pounds added should put you back around the 8ish rep range. From there, you can then get back up 10 reps with that increased weight and up it again. So on and so on for 8-12 weeks OR until progress stops. Then you change up the routine to something else which incorporates progressive load. Perhaps a lower or higher rep scheme or maybe even different lifts all together. Just be sure to keep things the same long enough for your body to recognize the motions, adapt to the increases in weight and overcome the goal. Don's change stuff too often or you will not progress.