I guess at that point you just need to start doing it. I have a lot of outdoorsy types in my family and we've been doing long, multi-day backpacking trips most summers since 1998. On my first trip I bought a cheap sleeping bag, pad, and backpack and relied on the more experienced people in the group for everything else. The shoes I wore were terrible and by the time we got back to the car on the end of the 4th day I could barely walk my feet were so blistered. For the next summer I saved up and bought a really nice pair of boots which I still have. They're the most expensive footwear I've purchased in my life and worth every penny.

I can't recommend enough finding a group of experienced people to start with. You'll make plenty of mistakes and they'll help keep it from turning into a catastrophe. You'll pick up a lot from them while also figuring out what does/doesn't work for you. Probably five years after starting backpacking with my family I was the 'experienced one' leading a group of friends on a hike through the Smokey Mountains on the Appalachian Trail.