Are you looking for 2k13 exclusively or any other games? I mean, you can get an ok gaming card for about $100 and sometimes even less, but budget gaming cards come with certain limitations if you want it to last for future iterations of the game. I'm thinking that the PC port of 2k14 would be similar specs to 2k13 just as 2k12 was since they will mostly likely be using the same engine, therefore you wouldn't have to spend a lot.
Edit: Just to give you an idea, here's a budget video card that will definitely run NBA 2k13 (and probably 14) without struggling too much:
http://www.newegg.com/Product/Produc...82E16814131477
But what you really need to be careful is that the card that you purchase is compatible with the rest of your system. It has to be within the Power Supply limitations, it has to fit the connections provided by your motherboard, and it has to fit your case. Higher end cards tend to be quite bulky and do not fit many pre-built systems. Be careful of making any impulse buys as you could easily waste your money and later find out that you need to replace several components to be able to install it.