>>54724660FireRed/LeafGreen is probably the best starting place if you care about getting references and understanding fanservice. There is really no reason to play the original Red/Blue unless you have nostalgia for them or genuinely enjoy buggy jank. This isn't me insulting the games btw, I like buggy jank, but the #1 reason those games were so successful is that almost everything on the original GB sucked even more than they did.
If you don't care about fanservice and references, you can start with HeartGold/SoulSilver, X/Y, Omega Ruby/Alpha Sapphire or Ultra Sun/Ultra Moon. These are all good starting places imo, although USUM is extremely heavy on handholding and cutscenes, which might be a turn-off, and X/Y is notoriously easy even compared to the other easy games in this franchise for small children.
If online features are really important to you, you can start with Scarlet/Violet because that's the most recent release, but these games are extremely buggy and run at an abysmal framerate, so they definitely will not leave a good first impression.
Also, in case you're wondering, the differences between paired versions are minuscule. In most cases it's just a small set of exclusive pokemon and sometimes a few minor detail changes, like the school uniforms being orange in Scarlet and purple in Violet.