As of right now, I have zero experience with shooting pistols lol.
get a 22 then. my buddy graduated from BLET in NC last spring and is now in LE, he used glock 9mm in the academy but his department issues sigs in 357sig. most likely you will be issued a department weapon when you get hired so logical choices now would be a 22 for lots of practice and/or something you could use as a BUG on duty. id personally recommend a 22 DA revolver, something that will challenge you to learn proper trigger control and sight picture as well as make whatever your issued seem like a breeze to shoot, and something like a keltec pf9 or one of the khar 9mms if your looking for a back up weapon