StingingVelvet: The original game's free DLC was good, forget the name of it. A nice little mission. The paid DLC was an arena thing that sucked, avoid it.
ME2 had a lot of free DLC you should get. Of the paid stuff Lair of the Shadowbroker is the obvious must-have. Project Overlord was probably second best, pretty good but not essential by any means. The Kasumi one and Arrival were pretty meh, you can avoid those.
You should get From Ashes for ME3 with that pack, which is good. I have heard Leviathan is good and Omega is bad, but I have not played them yet myself.
P.S. (Essential PC gamer superiority) - The original game is pretty horrible on Xbox, if you have anywhere near a gaming PC might want to at least play that one on PC.
Thanks...didn't realize the 1rst one played so badly on XBox..bummer., My gaming pc is getting a little long in the tooth, which is why I went with the XBox trilogy. The first is old enough, my rig might run it okay, but wouldn't be able to carry the game (save/character) over to the second one then. If it's that crappy on XBox, might give the 1rst one a go on the pc anyway...thanks for the heads up :D