If you are like me and you are sitting on an insane amount of GP (I have over 20mil atm), one way to speed up your leveling progress is to just buy players from the store and release them as XP fodders.

For example, Pedri is the cheapest 5 star player you can get for 96k(10k EXP trainer), and Gavi is the cheapest 4 star you can get for 39k(4k EXP trainer,) and you do get some GP back from releasing them too. I wouldn't recommend this if you have a limited amount of GP and I really wouldn't go crazy stocking up on trainers, but if you feel the need to build your first team ASAP and you are running out of carry-overs to release, I guess this is one way to do it.

Even if you aren't maxing them out right away, you might notice a pretty big difference in how the team plays by just leveling your players enough to increase the overall team play style level to 90 .