Coinbase allows you to buy Bitcoin, Ethereum and Litecoin, so which one should you buy?
My advise is to buy all 3, in order to diversify.
When I first got with Coinbase I started buying only bitcoin, back when the price was $800, and Ether was $8; however I was solely focused on bitcoin that didn't buy Ether because the price had been so low and I didn't think it would go up,
and missed out on some of the early gains.
After seeing the price of Ether jump to $40 I got in and started to do my research on Ether and realized that I could go much higher, and it did. It went over $400, but has recently dropped to $300 which is still several times higher than what I paid.
So then as soon as Litecoin was added to Coinbase, I decided to buy some, since it shares similar characteristics with Bitcoin, I see that this coin has future potential.
All 3 of these have gone up in price, so by diversification I haven't missed out on gains from other alternatives to bitcoin, although Bitcoin makes up 70% of my wallet.
If anyone is interested in getting started with Coinbase here is a referal link, When you buy $100 worth of bitcoin both you and me will get $10 worth of Free bitcoin.