Training

I started swimming "seriously" about a year ago and usually swim 4-5x a week (one hour workouts) with my local masters team. I'm already pretty fast, but I am trying to make the jump to being very fast. Since I'm fairly new to swimming, I'm not really sure what would give me the best results: more volume or more drills/power work or both? Would doing dryland training help too? Perhaps doing longer workouts? I really don't know much about training theory etc when it comes to swimming, so if anyone could offer some insight or point out some good articles or books that would be greatly appreciated! Thank you!