Getting the free apps below will give you $10 in free coins, to get the other $13 follow the instructions below. Even if it says device invalid you can still get the apps and get the free credit, just "purchase it" but don't install them (this feature works on computers, but may not work when trying this from mobile)
NOW TO GET ANOTHER FREE $13 IN COINS!! (if you already did this you can't do it again): Amazon has another offer I posted yesterday here for a free $20 credit when you buy the Game Grand Theft Auto for $6.99. SO.. After you get your $10 in free coins above CLICK HERE and buy the game for $6.99 with the coins you just got so it is free for you. You will then end up with another $20 in free coins - the $6.99 spent. $10+$20-$6.99= $23.01 in free coins!!