It was 1985. I was but a wee lad. I had utterly succumbed to the obsession of TSR's wondrous pen and paper masterpiece ... Red Box D&D.
The first store I purchased products to further my addiction was from a book store actually. Called Waldenbooks. Sadly the entire chain went out of business in 2011 I believe (I think Borders bought them out some years prior to that ... I don't recall for sure though). Anyway my purchases were limited more by the stores supply than my bankroll. At the time I was an independently wealthy paper route tycoon. I had two seperate paper routs, a lucrative lawn mowing busiess AND I helped my neighbors "buck" bails of hay (i.e., toss hay bails up on trailers and then stack them in the barn). So for a 10 year old kid I was loaded. Money to burn and an addiction to feed!
I wasn't the GM though so my needs weren't very great honestly. I mostly bought the classic brown "complete" series books. I bought issues of Dragon and dice when they were available. Never really got to buy minis as the store never carried them .. sadly.