I first started off with Coinbase and has since stayed with it till now. Coinbase is very user friendly and easy to use for beginners to start trading with BTC, ETH, LTC and BCH. Previously the sign up and verification were easier and takes shorter time but for now they are more strict and taking more time before you can make a high amount of purchase.

Overall I would recommend Coinbase to those new to cryptocurrencies. Its a good place to start!