I just started mining recently and this is what I did.
If you want to mine the scrypt coins like LTC, FRK, FTC and most of the other "altcoins" then you compare the price of the hardware with the hashrate it produces. I personally ended up with 270x because they get alot of bang for the buck right now.
Here is a hardware comparison guide.
https://litecoin.info/Mining_hardware_comparisonThen you have to determine what sort of mother board you want, ram and hd arnt really important in mining. Basicly the gpu's are the most important thing. And a power supply that can run them all.