.So... what exactly are you planning to do with this? That usually helps in deciding parts.
In general, clock speed (the gigahertz number) tells how many times per second the cpu/gpu or other part will do a certain process or set of processes per second. RAM or VRAM is generally how much info can be stored temporarily. Cache size is generally how much info the CPU can store by itself and process. More is better in all of these, but have to be balanced against price. Some general things to know.