Drebb, Fantasy Grounds College is helpful for people who want to just be players, also. They support multiple games (I've had classes in Starfinder, D&D 5E, Savage Worlds, Call of Cthulhu). You may see more things involving D&D but a lot of what you learn in those can be applied to other systems, also. Especially if it is centered around how to use things like Combat, creating characters, etc.
As for rules familiarity, I do not think it is necessary. There are introductory adventures. I always let people know my experience with FG (some) and a ruleset (D&D 5E: a little).
Everyone has been very helpful, also. I've seen people have questions and they get answers quickly via text chat or even via impromptu voice chats.

