I didn't make a business of MTG until the end of high school and first part of college, ~1999.
eBay was new then, and an older friend showed me the prices on eBay and told me how to make money buying/selling. Since I was traveling to go to the Pro Tour/etc, I had a lot of opportunity to buy cards to sell... mostly bad cards from good players that sold well to casual players (think big dragons).
It's been so long I can't remember. Most of my cards came from Revised because that is what we sold and unboxed, so I basically had all the most powerful things from there like the Serra Angel, Shivon Dragon, Wheel of Fortune, Mana Vault, Copy Artifact, Demonic Tutor, Vesuvan Doppelganger, Winter Orb, Armageddon, Mana Flare, Will O' the Wisp, and all the multilands, which is what made a five color deck possible.
Then I had a few strong creatures with trample damage, and a few Limited and Beta cards that I had traded for like a Time Walk and Ancestral Recall, and at least one Mox.
But I never had a Black Lotus, although I almost got one once.