My favorite exchanges for bitcoin beginners are Coinbase, Gemini, GDAX, Bitstamp, and CoinMama. The lowest fees for U.S. residents investing in bitcoin are going to come from Gemini and GDAX. I think Gemini is the best balance between simplicity and fees because it has a clean trading interface and low 0.25% fees. You can get even cheaper fees on GDAX, which has a beautiful full-scale trading interface that I love, but you need to spend a few minutes learning how to use GDAX if you've never done any trading before.