Go onto CSGODouble and sign in with steam, then press "Free Coins" at the top and use the code SKE555 to get 500 coins for free ($0.50)!

By doing this SKE will get a small amount when you bet on CSGODouble - there's no down-side to using it and I personally use CSGODouble as I can bet for CSGO skins without having to actually deposit them in the first place, just by using this code. I've already worked my way up to 3000 coins by starting with just that 500!

Give it a try!