I have barely needed a second pair of JoyCons. But that's because my cousin lives really nearby. When we play Super Mario Party, he has JoyCons too. So you probably want 2 JoyCons. Or if you know you're getting an extra dock and extra JoyCons anyway, maybe consider 2 Switches. That's only if you have plenty of money.
I would say get at least a 128GB microSD. If you know you're getting a ton of digital games (especially full retail games digitally) go for 200GB or 256GB. I have a 128 GB microSD and still have about 80 GB free.
I think you're at a good time to get a Switch. If you waited until the holiday season, there would be other huge games coming out. Your backlog would get even bigger!
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 122 million (was 105 million, then 115 million) Xbox Series X/S: 38 million (was 60 million, then 67 million, then 57 million. then 48 million. then 40 million)
Switch 2: 120 million (was 116 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
