What are you looking to do? I think you really have three possible paths in crypto:
If you just want to play it safe and likely 3-5x your money, just buy and hold BTC/ETH/LTC for a year or more. You'll also get the benefits of LTCG tax rate.
If you want to add a slightly higher risk profile and take some measured gambles, you can add a few of the big "altcoins" into the portfolio (think Ripple, etc.) But you'll have to expand onto other trading platforms beyond Coinbase for that, although the major ones are still pretty easy to learn quickly. Binance is a good one.
If you want to shoot for life-changing returns (10-100x gains) then you'll need to diversify out into more obscure altcoins--and in order to get them you'll also need to learn how navigate the tertiary trading platforms, which *might* come with higher risks of fucking up and/or getting hacked (although I think that is overblown if you are smart and careful). EtherDelta and Kucoin are two that you'll hear about on this level. The other issue here is that technically every coin-to-coin exchange is a taxable event... which quickly gets insane and totally unmanageable if you're trading a bunch of little altcoins on a regular basis...