Welcome, to the forum and to the addiction.

You will need to read the articles here and elsewhere - Mark Verber's site is my first suggestion for anyone getting started, it's a great primer for gear selection.
http://www.verber.com/mark/outdoors/gear/index.html

Pack last, gear first. You will probably want to look at the gear lists here on the home site of the forum, at Mark Verber's, and start thinking about tradeoffs - you need to consider your destinations and the weather and climate you will be packing in for the first little while, and choose appropriately. My gear is tailored for Sierra hiking in spring, summer and fall, and coastal hiking in winter. I have to be prepared for 20F-30F night temps all year long. I doubt I would be comfortable heading for the Rockies without serious consideration of the differences there - I'd be adding bear spray, for example.

Not knowing if you are wanting to go light or ultralight first off, I suggest aiming for a pack weight of 30-40 lbs to start. Finding a good balance between comfort, safety and pack weight will help make outings pleasant and less prone to aching back and/or feet. You will find a great variety in "needs" among backpackers.

Don't assume a tent needs to be waterproof to keep moisture out. It needs to provide you with adequate shelter to keep your gear dry in rain, but be ventilated enough to allow condensation to evaporate - that's a tough thing in some environments. It's also a consideration with rain gear. My typical setup is an open tarp with a hammock strung under it, and a poncho for walking in the rain. Condensation has only been an issue while camping in a river valley near grassy meadows.