hey im Not from a hardcore raiding guild i have rerolled server to join my friends and play with them. and we did bring random ppl that just dinged to 80 into our naxx raid. we did clear 3 wings and was unlucky on the last boss we tried "Grobulus" had 5 dc one each try so we decided it wasn't our night and stopped.
but to my point as for a starter i would say go for:
Plague wing 1st. = north , hiegan and Loatheb. the only prob could be hiegan if you not have tried the old naxx

and Loatheb is also a little prob without a priest with CoH. but we did manage to 6 man both hiegan and loatheb on about 13 mins on both kills. after that i found Deathknight's wing easier than spider wing dunno about it was my guild that was completely slow to learn tac. but anyway DK wing is easy first boss there we toke on first try (ravious). gothik is the next in DK wing. hes pretty hard because you have to constroll your dmg but a good addwise have a pala tank on undead side (if you have no pala, then take your best tank that side) 4 horsemen is easy you just have to learn the tank switching. and have a healer and a dps tank the 2 ranged so you have 1 dps more for the melee horses.
and then i would say go spider wing it's easy if all just read what to do our porb was that ppl dont even read. thats one thing but they can't expect RL's to tell them if they dont listen. (2 second boss i would say is the easiest in naxx) the only one there is that easy too is patchwerk in the next quater. and if you just have the dps and 1 warrior to tank and the last boss i have tried is also easy we was just onlucky with the dc'ing tank and healers (on grobulus). but yea why dont go abimation wing first when patchwerk and grobulus is easy thats because of the 3rd boss is very very hard. hope this help you go for it and GL