Ways to drop time in the 100 Butterfly?

But i really want to be at 54.30 so i can qualify for Highschool states. I started doing pushups everyday, pullups, and 4 rounds of 30 seconds of stretch cordz work My problem is that when i train at practice i dont know what i should be going for 25s , 50s and 75s. For example our coach puts 50s on 40. What should i be holding for each 50? 25s are sometimes put on 15,20 and 25, 75s are put on 50,55 and sometimes a minute