Coins are needed to repair weapons and buy new weapons for their player's class. They are not that hard to obtain in the game as challenges and matches reward a decent amount. You can get twice the amount of coins received in a match by buying a coin booster pack, which costs 25 diamonds (the same goes for a diamond booster) and lasts one day (24h). It is advisable to only use this when. Being a VIP member gives you a lot of extra coins per match as well.
How To Get CoinsEdit
For winning a match, you get 2,000 XP, for losing or participating, you get 1,000 XP. The amount of coins depends on the amount of XP you received during that match. At the end of each match, 10% of the total amount of XP will be counted as coins.