I never played the series but I plan on getting into it. Do I just buy all the games in order of release and thats it or are some of them not really related?
Well they're all related (with the exception of AC3, which is the start of a new character I believe). However, if you're just getting into it and want to save some cash, I would say skip AC1. I'm sure you could look up the important story elements.
It's not a bad game per se, but it pales in comparison to AC2 and beyond. There's way less side quests, and you basically pick from a few activities to gather intel, then do a major assassination, rinse, repeat for the entire game.
Though if you have the money and think you're going to play through the entire series, it may be interesting picking it up. At the very least, it will make you appreciate AC2 (and especially brotherhood) way more.