So I upgrade...bringing in larger quantities...stacks of 50-100. (I occasionally would sell as many as 100+ in a week, making over 200mil profit on just that one item.)
Of course, by this time, I was completely hooked to trading and started experiementing with other items, buying stuff off contracts...pushing up prices by buying items that were already in the station I was trading in and putting them back up at a higher price.
Some things worked...other things didn't work. I experimented and 'played' around with my isk until my measly <100mil (I was always grinding missions and ratting to get enough isk to pay for my pvp ships) turned over into plus 1 bil numbers.
And that's just the beginning.