Follow this link: https://www.coinbase.com/join/titoua_a by registering through this link you will get $ 10 of bitcoins for buying or selling at least $ 100 of digital currencies.
Click on the Coinbase referral link then create your account and you can start using coinbase and buying bitcoin, ethereum and litecoin. The 10$ coupon code will be automatically added to your wallet once you have trade more than 100$. You can share you coinbase coupon link & coinbase voucher to invite your friends and get 10$ of free bitcoin when they activate their account.