First gaming convention you ever attended? It was Gen Con 1993.
I didn't have the best time. For one thing, I wanted to try new games the we didn't play in our group and my two buddies wanted to play Marvel Super Heroes, ADnD, and Champions. I really didn't want to go to games by myself, but I tried and realized gaming for me is about hanging out with friends (something that would haunt me for years to come).
Magic: the Gathering premiered there and all of those "jackasses" at Wizards of the Coast's booth kept me from buying a copy of Quantrigue for Talislanta. Just from it, at the Hero Game booth, Sean Fannon, who is a master of customer service, was so hyped for the future of the Champions line, that he promised their booth would be bigger than the TSR Castle.
I did score a limited edition preview copy of the Alternity Player's Handbook...and never played it.
I will admit that gaming conventions are not my thing, too many unwashed masses and sensory overload really cause me a great deal of anxiety and borderline depression.