From what you've explained, there are a few things you should look into getting, repairing or retrofitting for your bike as inexpensively as possible.

1. Panniers should be near the top of your list. You can get a decent pair relatively inexpensively or you can spend a lot more for complete waterproof features. Your choice. Panniers will mean you won't need the backpack or the bike bag.

2. Look at your rear flashing light. It will probably have a clip which you can use to clip to panniers, a rack bag or your clothing. If not, you can fashion your own clip. Get an alligator clip at the electrical department of your hardware store and glue it to the back of your flasher using epoxy. You can now clip the flasher to almost anything (but you won't be able to use the seat post mount anymore.)

3. You can get a basic front light for less than $20. It will double as a flashlight. There are also some sites on the Internet where you can get information on building your own lights if you're so inclined.

4. Before your next tour, take your bike in to your local bike shop and get it tuned up. The people there will be able to get you ready for the road and they'll know exactly what your bike needs. If you don't need a new seatpost, wheels or derailleurs, don't bother getting them.

5. Going clipless is nice, but it's not an essential. I've done tours with them and without them.

Your camping equipment needs will depend on how you want to travel, but at the very least, you should have a tent and a cheap mattress pad in addition to your sleeping bag. For the first tours, as you're learning, borrow a small tent from a friend. Or see if you can find a second-hand tent at a camping consignment shop.