Play scrims / pugs / lobbies, any sort of competitive form of game with the class you intened to improve at.
I play Soldier (roam) and found out, that the more you actually play the game, and practice rollouts in an actual game, you can get to a point where it's a simple thing to do.
You also improve in gamesense and communicating with your team, and learning which calls are the right ones to make.
MGE is purely for DM, it makes you better, no doubt, you should play at for a while, if you have a match and you got some spare time before the match, and you think you're not warmed up or something, play some MGE, it'll get you warmed up quickly.
Jump maps are good, very good, but most of the jump maps aren't that useful in-game, create an offline server and start practicing jumps & rollouts, think about new and cool ways that you can play a certain map or get better at the jumps there.
Play a match, check which jumps did you fail to do, or which ones you should have done, practice that specific jumps and you'll see you'll get better.
tr_rollout (or whatever it's called) is a good map if you want to practice rollouts offline.
TL;DR My advice, play the game, for me jump maps are purely for challenge and fun, MGE gets you better in DM and it sure helps out when it comes to in-game battle, play it often, and you'll see that in-game you'll never have to worry about trying to score an airshot or win a 1v1.