I think I'll be there before anyone else.
I guess you could look at enchanting with the most expensive enchantment you have to get a little more gold out of the deal in order to buy more gems, but that is really micro managing.
I usually don't bother with enchanting that much until I get to level 25 or so. By then I have collected a slew of soul gems and then spend a day or two roaming the range around Whiterun.
I want to say it takes 250 enchanted items to get to 100. I could be horribly off but that number is flashing in my mind for some reason.
EDIT : Ah... I was off by 60. It takes 310 soul gems to get from 15 to 100. Maybe I was taking it from 20 to 100?
At any rate this is what I usually adhere to...
Petty / Lesser - Enchant to level
Common / Greater - Recharge weapons and staves
Grand - Enchant gear you actually use