Although the option to buy Madden cash is always available it is not necessary to spend real money to get your Team to where you want it to be. If however you want a full team of Gold players immediately because you are not patient enough to grind things out you will have to put your hand in your pocket. The game has a Stamina system which you can instantly replenish using Madden cash when it runs out if you want to continue playing without having to wait.
Scams
Don't be fooled by the unlimited coins and Madden cash scams and hacks that are all over the net for Madden Mobile. EA have now patched all the glitches that were once in the game so nothing like getting duplicate cards now exists. Don't waste your time looking.