For me, my personal Indy canon is this:
Temple of Doom
Raiders of the Lost Ark
Last Crusade
Fate of Atlantis
Crystal Skull (TM2YC Edit)
EU novels will be added as I read them
Definitely the first three films, though I pretend Temple is set in 1937 instead of '35, as it doesn’t work at all as a prequel to Raiders (Indy’s a skeptic in the first film, which makes no sense if just the year before he experienced first-hand the magic of Mola Ram and the Sankara Stones). I also include most of the comics. That’s about it.
Gods for some, miniature libertarian socialist flags for others.