The best way to get this is after you have completed World Tour do the following, but first MAKE SURE to not accept any "real players" from challenges that you have done in the last two stages. They can only be "fake" or "created" players on your team. You have (1) spot for error as your team holds 9 people.
After world tour my character was knocking on the door of 50, and the people that I rolled with in every game were around 40-42, quite a lot of boosting left.
So, when your done with everything else, the best way to get points is this.
Hit the Streets > 5-A-Side (two controllers) > First Controller choose your team Second Controller choose any team, but maybe lower I chose Granada from La Liga > Easy, Timed Match (Set the Time to Whatever you Feel Like), Random Map.
Your Lineup should include all the people you still need for 50. Make sure to have one person have an aerial ability, I used Rainbow Flick (<- RS, RS ->) which is unlock-able.
Go into the match, isolate one vs one on your best player against their shortest player. I used three tricks Panna (through their legs), Rainbow Flick, and Juggle (RB + LS towards defender, should pop the ball over their head). If you do those three tricks in any order, you should be getting around a Freestyle score of 800 each time you do one trick. I noticed the score would go down if you kept doing the same thing over and over, so just alternate between those moves.
Using this method, I got about 20k style points for 3 minute halves. This goes to one player, but also levels up the whole team some, and even the bench. So rinse repeat until everyone is at 50, and change out players as necessary to get the others to 50 that were on the bench.