There are no cheats on fifa superstars app,however a good way to build up a good team is to buy extra premium cash to purchase any deals that they are doing. I.e. I have just done this and as the euros are going on at the moment they have a deal every day, so I purchased some premium cash and bought 2 platinum french players for 100 premium cash.
Training
Training is the percentage of team talent you use. Try to train every 4-5 matches, as this will enable you to get the most of your matches. You will also get more if you level up.