Ways to gain experience: search for hiking clubs and meetup groups in the nearest population centers to your home. Those are a good way to start. Google or other search engine is your friend! You'll learn a lot and meet new friends and possible potential backpacking partners. If there is an REI or EMS in your area, they often offer classes, as do many clubs.

Don't buy too much too soon, and wait to buy your pack last. Your pack must fit your body, your gear and be comfortable specifically for you with specifically your gear inside. Pack fit is almost as individual as shoe fit!