Quick story, as Gen Con looms.
When I went to interview for a staff job at Wizards of the Coast in 1999 (they flew me from OK to Seattle), I wore a suit. Slacks, dress shirt, tie, jacket, black shoes, the whole 9 yards.
One of the things everyone made VERY clear to me during those interviews was that WotC had a casual atmosphere, and there wasn’t really a dress code at work. I felt overdressed.
OTOH, I a: got the job and b: later heard that another candidate showed up in a fast food uniform. No one ever told me that made a difference… but no one said it didn’t. And one person tad me that the fact I showed up in a suit proved I was taking the job seriously. I have never regretted wearing a suit to that.
When I went to a dinner at GenCon that Sword & Sorcery was having to see who they wanted to work on the EverQuest Tabletop RPG, I wore a polo and jeans. I didn’t feel either overdressed or underdressed, and I got a lot of work from that meeting. I have never regretted wearing a polo to that.
I always recommend looking professional and tidy, and give the impression you take every opportunity professionally and seriously. If you later get told you can dress down, feel free.
But first impression really can count.