Welcome to HPA!
Absolutely a great sport to enjoy. It is a huge subject, with MANY books written about it, videos too, and entire forums. I've been backpacking about 40 years and actually present a seminar on wilderness backpacking in Alaska. I'd recommend going to Barnes and Noble and browse a few books. I looked up Westmoreland Co and it doesn't look too far from Pittsburgh. There is an REI store in Pitt. The employees there will have a wealth of knowledge, they are very accomodating(required), you probably could spend a couple hours there and learn a lot.
Being a hunter I combine hunting and backpacking, usually in Alaska. But a lot of trips were also just backpacking. As with any recreational sport the prices on everything can range from expensive to insanely expensive, with backpacking it is dependent on the lack of weight of an item. Almost always I go solo and for 7-10 days my pack as it is on my back weighs about 75 pounds. Of course shorter trips reduce food weight and multiple people can share tent, stove, fuel and some other common items. On short solo trips you would need to be physically prepared for carrying at least 50lb.
I guess major purchases would be something like this, in the beginning for a warm weather overnight trip you could make do with less technical equipment, maybe whatever you have now, but eventually you'll want all of the items below plus many more minor items like cookware, lighting, emergency items, etc:
water filter $10-$125
sleeping bag $75-$300
sleeping pad $20-$75
lightweight fast drying synthetic shirt/pants $60-$150/set
gore-tex or similar jacket $75-$250
rain pants $60-$125
I have a 4 column 3 page master checklist that includes everything I've ever taken on any hunting/backpacking trip in the last 30 years. For each trip I open it up and start deleting everything I will not take, what is left is what I take. It's so easy anymore and it's 100% reliable. I just add new items as I buy them.
Just FYI, I have a used Sierra Designs Polaris tent I have no use for anymore and would sell. You can google it and you will find it is/was a highly regarded tent. If interested please pm me. I probably could use an inventory reduction on a lot of things.
This is a few backpack vids with the tent. First 2 are from a trip with my daughter about 250 miles north of the arctic circle in the Brooks Range. This trip was about 10 days, my pack was about 80lb and I think hers was about 35-40.
This one is mostly about the caribou handling but towards the end there is a little of my stove and the Sierra Designs tent, you can also see my backpack that can either be used with a bag or without as a freight hauler: