Most important gear:
solid pair of heavy duty gaiters--keeps your boots from getting dirt and snow in them
sleeping bag--not only is it where you'll spend at least a 1/3 of your time, it's also what will keep you alive in an emergency and doubles as a way to keep your gear dry (wear wet gear from the day inside out or lay it on top of you inside the bag)
camp stove and aluminum cookware--dont skimp on these... needed to melt ice for every meal and refill waterbottles for everyone on your hike
everything else is negotiable. a nice thing to pick up is a couple sea2summit dry bags for all your clothes and 2 heavy duty trash compactor bags to line your pack with. when it comes to your gear, the #1 battle is moisture. I prefer very thin base layers as they can dry by themselves once you stop sweating simply by the heat of your body. shell layer, get something gortex by a major brand and youll be fine. then add insulating layers in between depending on how cold you are. make sure you have enough thermal layering for a worst case scenario... you will probably never use it, but you can go from nearly overheating on a steep ascent to nearly frostbitten when you go through an opening at the peak where the wind is forced through, so make sure you can reach it quickly.
last but not least, make sure your boots fit!! happy trails