Coinbase is OK for holding or withdrawing coins to USD, but it's not a good place to trade. For that you should consider bittrex or bitshares - the latter is better, but a little more complicated.

I can't tell you what coins to trade... I really don't know. All I'm holding right now is steem and LBRY, but your mileage may vary. I'd recommend looking at one of Steem's day traders, there are a few good ones who can offer you advice there.