Buy a 161 in 1 now and set a reminder for the neo sd or pro when they’re back in stock.

Of course, that’s more of advice for playing the Neo Geo and less about how to collect for it. Assuming we’re talking MVS, if you’re after authentic carts know that there are several types of bootlegs out there…some are brand new reproduction boards, others harvest common games for authentic boards but use new/reflashed chips as well as mods to play a different game. Both types of bootlegs can either have sound or graphical issues or work perfectly fine. Try to only buy games where you can see the boards, do research on scans of boards and labels. The nature of these games originally being used for arcades, sometimes labels and shells have been replaced on authentic boards due to wear and tear.

MVS is also region free, your motherboard will decide the region/language the game plays in.

Only you can really decide what type of collection you want.