>>22172637You could probably afford Sky and Red if you have something to play GBA cartridges. Red is Blue but without bottom screen, which I never had a problem with. Obviously Blue is the superior version, but just barely. You don't NEED the extra screen, it's just a perk of the DS version.
If you really only have enough for one version, just go with Sky. Has a fun story (story in Red/Blue is still really good), more pokemon, more content in general. You can't really go wrong, they're both good.
As for Gates to Infinitey, I got it for Christmas and barely picked it up afterward, if that tells you anything. No fun personality quiz to choose your pokemon. 3D isn't really that great. Probably still ok, but play the other two first to get the real Mystery Dungeon experience.