Coins are an in-app currency that is Long Game's way of rewarding you for saving. You can use Coins to enter into instant games and the weekly drawing.
You earn Coins based on how much you are holding with Long Game. Coins are earned on an ongoing basis based on how much money you are saving in your Long Game account. This means if you are earning 170 Coins per week you will see 1 Coin added to your account every hour. Similarly, if you are earning 45 Coins per week you will see 1 Coin added to your account about every 4 hours.
Additionally, you can earn Coins by referring friends and accomplishing savings Missions. You can see full earning rules here: https://www.longgame.co/terms-conditions/coin-earning-rules/