Also does anyone have a Soulgem guide? I don't want to keep wasting soul gems.
About soul gems and enchanting, if you want to make money with enchanting, the best enchant that i found so far is the "banish" one, but i think that you need to be high level to find it in shops. Anyway, once you have it, you can make a lot of money even out of petty soul gems (but note that for some reason, the price of self-enchanted goods seems to drop as you go higher in skill, even though the enchant itself gets better). Previously, my best enchants for money were Absorb health and before that, Turn undead.
Enchant iron daggers with that and you'll get monies (and of course you'll train your enchanting skill).
Now, the biggest problem that i faced when training enchanting was finding enough petty soul gems for all those 1 hit point wonders out there. The easiest way seemed to be checking the shops often, and in particular the college of Winterhold, since you can get soul gems from half of the mages there. When out hunting for souls, i always have with me a weapon enchanted with soul trap (1sec), and finish the creatures with it (i sorta roleplayed mine as a sacrificial dagger). Even a low level soul can make a good soul-stealing enchant with many charges, because of the low duration.
Petty/lesser/common/greater souls should be used on vendor trash to train enchanting, while Grand souls should be kept for your best equipment. Here's a quick rule of thumb for soul ranks, from my experience :
Petty : most animals (deers, wolves, skeevers, foxes, goats...), skeletons, regular draugr...
Lesser : low-mid tier of monsters, basically most semi-dangerous-if-unprepared monsters.
Common : dangerous creatures at low levels : Frost trolls, bears, mini-unnamed bosses..
Great : Giants, some dungeon bosses.
Grand : Mammoths and Dragon priests. At my level of progression, mammoths are the most reliable source of grand souls, but there are probably some other tough creatures out there with grand souls.
When i'm hunting for souls, i make sure to have at least 15 petty/lesser/common soul gems, 5 greater, and as many grand as i'll be killing mammoths. If i'm not hunting souls, i only keep the Azura's star, and i recharge my weapon with it as often as possible.
Edit :
I just read the wiki about the Black Star, i'm kinda disappointed to learn that the black version can also trap "white" souls, unlike what the game tells you. It makes the normal star inferior in every way, even though i'd still take it, for roleplay reasons. But i'll definitely take the black one if i make a new, more sneaky character.