the next step? preparing over summer f/ 400 and soccer

k, so i just finished my first “real” track season. was hampered by sickness throughout, but at least I was able to get to practice/meets consistently. Did the 400, ran a 60, 58, 57, and then 56. the last three times occured within the last 2 weeks.

I just turned 16, am 5’6 and 130 lbs. Strength/muscle mass is obviously the first thing that needs improvement (i always seem to die out by the last 150), followed by figuring out how to run the race form/strategy wise.

Question: How should I go about preparing over the summer? I have soccer tryouts at the end of july as well, including some pretty harsh conditioning for a month or so(our coach went through college on a cross country scholarship). Last season this featured stuff like 100 50yd. sprints, and then some longer sprint work. I’ve never really committed myself to track/a sport before, but I really wanna get down in the 52 range next year…a bit “farfetched” for now, but there’s a lot of room for improvement.

And just some more info, soccer coach will be timing us on a 2 mile, 100yd and 50yd as well. not too worried about the 2mile, but for the sprints i’ll be up against bigger/stronger upperclassmen.