What’s a good place to get anime figures/anime/game collectors editions?Watch
In terms of collecting anime, which I presume you mean blu-rays and DVD's, HMV, amazon, basically anywhere you can buy discs from. CEX also sells used DVD's/blu-rays for things that are harder to find.
Game collector editions are a bit trickier. Most of the time, you will need to pre-order them from Amazon or Game before the release date- right now I've got a pre-order for the Nier Replicant White Snow Ed, and I pre-ordered it back in September/October, and it releases this April. You need to be quick with these, because even with pre-orders, the stock finishes fast.
Some game companies like Square Enix have their own online store where you can pre-order collector editions of their games, and get merch from their franchises too.
If you really wanted a collector's edition but it's gone, ebay and CEX is the only place I can see you finding it after they're gone. Normally, they are priced much higher than they originally were, and in terms of CEX, may not be in perfect condition.
I hope this helps!