To mine seriously you'll want to look into GPU mining because CPU mining is all but dead, and GPU mining while still possible from home is only good when it comes to ASIC resistant algorithms. Forget about SHA 256, Scrypt, and anything that you can use an ASIC on.

My suggestions would be to find a good mining pool, and shoot for maybe Ethereum while it's still POW and not POS. The Cryptonote algo is also a good alternative for home based GPU mining just don't expect to get rich anytime soon without a server farm and watch the Hashrate per Kilowatt hour because the bills can all but kill your ROI when mining from home.

Trust me, I've been doing this a long time and we're nearing the end of the home based GPU miner in the very near future. If you're dead set on it as a hobby or learning experience I would highly recomment researching a lot before committing to buy any hardware.

Some (actually most) algo's are best run on an AMD card but others do well with Nvidia cades if not better. Pick your coin and algo first before buying anything. Nothing sucks more than paying hundreds or thousands of dollars on hardware only to find out mining isn't like gaming.

The newest most expensive Nvidia cards are hardly worth the cost if you're going into mining and the money would be better spent on several cheaper cards in one machine, rather than one single high end card meant for gaming.

FYI : I'm posting this from a mining rig as we speak. lol