Magic: The Gathering

People have mentioned Pauper and Commander as formats, both are great and can be cheap if you and your friends aren't tying to play the meta. I wanted to also add that formats such as commander also have a variety of game styles in them to add variety and complexity. Such as 3 headed giant, Planechase, and one I saw recently where an additional treasure/Curse deck is in the game that players can grab a card for a permanently increasing cumulative cost.

Beyond all of that I would also recommend proxies for in-person play if everyone agrees with it for variety and cheapness. It can be as simple as printed pictures in sleeves

Games are always extra fun with snacks too, like Bugles!