Cable confusion?

Hi everyone, I hope some one can clear up some thing's I don't know about cable. First of all, I did try look up past threads on these questions, but was unable to find the answer's I was looking for, so please forgive me if these have already been answered. I know this is annoying to the "regulars". I know gauge refer's to the thickness of cable, but which is better for speaker cable?
A lower gauge cable or a higher gauge cable? I currently have two systems, one for HT, and one for audio. I currently use Monster XP cable for both systems. From various threads I've read, no one seems to use Monster cable for speakers. (Yes I am a novice) The best High end store around me (within my budget) is ultimate electronic's and that's all they sell.