Most popular do seem to be ethereum, monero, and zerocash (at the moment). Why not research those three coins and see which one interests you? If you are in it for profit, you sadly will find out that unless your hardware and electricity is free, it is most often (for hobbyists like yourself) much smarter to buy the coin outright and wait for the price to appreciate.
In terms of electricity useage, ETH uses the most, ZEC the second-most, and XMR demands the least amount of electricity (if that matters to you).
Have a great time mining!
Websites that I find interesting..
cryptowat.ch
coingecko.com
https://anorak.tech/ https://monerotalk.org/ https://forum.ethereum.org/categories/mining