There’s a lot of guides on the web regarding this subject! we’ve tried most of them! Some of them are very time consuming, some aren’t! I primarily use 4 ways to earn FIFA 15 coins.
No 1: Exploiting tournament system
I dont think this will be pacthed. But in FIFA 14 you would only get a gold pack for winning the tournament for the first time! In FIFA15 you will get a gold pack each time you win! Furthermore its pretty fun to play tournaments, and you dont have to spend money to get the thrill of opening packs! I mostly play tournaments. So playing tournaments (Assuming that you win it, will get you = 2.800 for playing 4 games + 2.000 for winning + gold pack (5.000) = 9.800 coins per hour! Assuming that 4 games takes around 1 hour）
No 2: Know when to buy an IF player (Make calculated risks)
In the beginning of FIFA15 I bought for example Miranda (IF). My thought was that only Sergio Ramos was better! Its actually still like that! So I bought him for 70k and sold him recently for 130k = around 50-55k profit on 1 player.
Making calculated risks and understanding the market: An IF player is always very expensive when he enters the market! Assuming he is worth using in the future! When TOTW is out each wednesday, buy the IF`s! If you want to try to invest and make profit on IF`s buy them monday or tuesday evening (A lot of the same player on the market, cheapest price!!)
They rules in my head: Buy IF`s whos actually usable in the future! Like Lahm just came out (Bought him for 240k assuming that he will be more expensive in 3-4 weeks, I dont use him. Its only investments! Furthermore, this aint at all time consuming (more time to play the game!)
No 3: Getting better at fifa! OBVIOUS! Winning tournaments and getting up in higher divisions will earn you more coins.