I followed this page:
https://litecoin.info/Mining_hardware_comparison, and it shows this to be the best graphics card for mining: 7990, HD7990-6GD5
Is this the best at the moment on the market? If so, can I use this to mine coins such as Dogecoin?
Yes this graphics card hashing speed is highest and can be used as gaming card as well, or resold later easily. Check your electricity prices first so you know when the graphics card can pay itselves