Did you watch the Anime? If so, do Red. The nostalgia is everything.
If not, do Black/White because there's so many Pokemon you'll never get bored and it's amazing.
If you don't wanna buy anything, every Pokemon game from the Gameboy/Gamboy Advance/Nintendo DS generation is easily emulated for free.
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Realo won gold at the Sex Olympics with a BROKEN FRIGGIN NECK.-Voltch