Glad to see someone your age getting into the shotgun sports.
I use to shoot trap all the time...#2 in state at 18yrs...and the only choke I ever shot was an improved modified. I would not go any lighter than a mod from about the 16-18/19 yd line. No lighter than IM from 19/20-22. And would recommend a full choke from there back. #8s are typically fine from 16yd to 20/21 yds and then would switch to 71/2s.
I always shot Reminton STS rounds...and still do for everything. What type of wads are you shooting and what type of reloader do you have? I can typically get about 10-12