Before 1990, less than a dozen. I played with a group at school and also with one at home, occasionally.
Before 2000, less than twenty. I joined the Gaming Society at University and settled with a group that saw me through all three years.
Before 2010, I started to freelance write and attend a few conventions, so I probably doubled again to around 40.
After 2010, I attended every UK Games Expo and Dragonmeet, before adding all the Garrison conventions and getting my own ongoing gaming group organised. Right now, I'd say far beyond 300 different people. Far beyond.