>>45989376All that really matters is that you play BW before BW2, other than that go nuts.
If you don't wanna play everything, you can pretty much skip all of gen 6. ORAS is more like a sidegrade to RSE than an upgrade, I'd personally recommend you play Emerald. XY isn't exactly bad, but it doesn't have much going for it. My favorite thing about it is the variety of pokemon in its regional dex, but SwSh BTFOd it in that regard. It's pretty mediocre aside from that.
We also might be getting gen 4 remakes soon, so maybe hold off on Platinum for a bit. If they aren't announced by February, you're probably safe to play it. If they do get announced, it might be worth waiting to see if they're shit or not. Wouldn't want you to get burnt out on the region if the remakes are worth getting.