usually i do 5 sets. the first 2 with fairly high repetitions. then increasing the weight and decreasing the repetitions.
The high repetitions are probably preventing you from gaining mass. The rule of thumb I've always heard (and also seen on this forum) is that if you want to tone and decrease your mass you lessen the weight and increase your repetitions. If you want to add mass and bulk, you increase the weight and decrease the repetitions. Also imo 5 sets is a bit much if you want to increase your mass.
Please someone correct me if I'm wrong.