There are many ways to earn FIFA 18 coins effectively. But which one is better depends on your own preferences as a player. Generally speaking, You can choose to play online matches, which makes you earn coins a little slower, or spend hours playing the market but earning coins at roughly twice the speed.

Whatever your preference, I would like to recommend you the two fastest ways to earn FIFA 18 coins in FIFA 18 Ultimate Team as below:

1. Gameplay: 4,000 - 8,000 coins per hour
It may sound a little unbelievable, but the best way to earn FIFA 18 coins that doesn't require you to pour hours into a virtual stock market is to simply play the game. You can attend matches, play coins boosts, complete tournaments and achieve rewards. Of course, there are skills to make it much more efficient though:

a. First, you can alway apply your coin boosts acquired through unlock different catalogue in the EA Football Club
b. Then, head to the Online Leagues. Not only will you earn at least 600 FIFA 18 coins for each win with the boost activated. Rewards there get into the low thousands, meaning that, if you play well, you can pick up several thousand coins per hour.
c. Another gameplay-based option is the FUT Draft mode, which with a 15,000 coin as entry fee, you'll need to do sufficiently well to actually make the FIFA 18 coins back.

2. Transfer Market: 10,000+ coins per hour
If you would like to spend none of your time in Ultimate Team actually playing FIFA, here's how you can earn decidedly more FIFA 18 coins than any other method free of charge. Mass bidding is the best method specifically, here's how to do it:

a. Find a player who's in-demand, but cheap enough to buy within your current budget. You're looking for a player whose demand exceeds the supply, but not to such an extent that you're forking out several million on a Team.
b. Find their average price, just cycle throught the card's menus where it's handily displayed for you. Then calculate the amount you'd need to buy it for, if you were going to make a profit by selling it for the average price.
c. Get bidding - Your aim now is to bid below the average price, by just a couple of hundred coins difference at most. Remember, this is all about your profit margins; you'll need to buy and then re-sell at a least a couple of hundred coins' profit each time.
d. Sell it - Assuming you got lucky and won a few cheapos, it's time to immediately flip them on the market. If you're staying with the game and want to re-invest your earnings right away, set the listing for one hour and the buy-it-now price as dead on the average. If you're happy to wait, set it for four or more hours and a few hundred over the average.