G1: A little bit of everything. Mostly ponies I wanted in childhood or my early collecting years at this point which is only a few now.
G2: Whatever I can find of the non-US ponies for a good price. I'm not actively collecting them but I don't really turn them down ether.
G3: None really, apart from the few I still have.
G3.5: If I find a big plush baby I don't have I will get it
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G4: Mainly Fluttershy, Discord, snowglobe ponies, some of the giant styling ponies and blindbags. Other than that I get one version of each pony if I happen to find it.