re: Increasing mass

How many pushups can you do? If you're doing more than 30 a set, I'd say start doing handstand pushups. You could still do high reps on the pushups sometimes if you want to maintain some endurance or you just like doing them, but making high reps a main part of your workout regimen is not going to be conducive to your goals.

Based on your goals, I'd go with "heavy" weights in the hypertrophy rep range.

Creatine hydrochloride for better absorption.