I usually start out with a couple warm-up sets of about 1/3 my working weight for the day. After getting loose and stretching in between those sets, I go to my working set weight. Say I'm doing 155 pounds. I'll do 4x6-8 at that weight and that's it for that exercise. Then the next week I'll either up the weight 5 pounds or try to hit the upper limit of that rep range. Once I can do 4x8, I up the weight - now I might be able to only do 4x5 at the new weight. I work up again to where I can do 4x8 then up the weight again.

You'd be better off doing 2-3 chest exercises rather than doing a ton of sets on flat bench. Do some incline bench with dumbbells, maybe some dips if you are able to. Dips are great for chest/tri development. I went from barely being able to do a couple regular bodyweight dips when I first started working out to now doing 4x8 with 55 lbs. added on. If you're looking for chest development, stick with the major compound exercises like flat bench, incline bench, and dips or decline bench with maybe an isolation exercise thrown in for variety every now and then.