Hi, I'm new when it comes to restringing my guitar, and i think I may have screwed it up. I had all my strings just fine, so I moved onto the low E string (.10). I was trying to get it to tighten, but I had issues with the string staying in place. I think I accidentally reduced the slack by a lot, because I got it to tighten but the string only loops around the peg once! I already made the mistake of leaving it like that and cutting off the rest of the string.

Is this bad? Will the string break easily or go out of tune more easily since it only loops around once?
I recommend anywhere between 1 and a half to 3 loops. It shouldn't be too bad if you have a nice set of tuners. Just make sure to stretch the string at the 12th fret or so to get it to set in place.
Yeah Dimebag is not the "Greatest Guitarist" of all time... Hendrix maybe... I must go get food to eat with my mouth

$250 for an amp? wow. is it worth it to invest that much in the amp?

Nah, as long as your tuning pegs are solid you'll be fine. It'll porob come out of tune for a bit until the string is properly stretched. Just keep retuning it and it'll stay in tune after a day or so.