One thing that binds everyone here is their love of being outside and backpacking, particulary light weight packing. From there you get into a LOT of opinions. I'll give you mine, for what it's worth.
The gear you have mentioned is typical of inexperience and lack of good knowledge. It is good gear. But you could do with a lot of different selections and a lot better choices for the same money. Except for the E+Light, more later. That pack is HUGE. I carry about 2500-2800ci for about a week out. The Rainbow is Huge. Nothing wrong with it though. Just bigger than you need for one or two people. The synthetic Slumberjack is cheap, OK, maybe you cannot afford better, but it will only last a few seasons.
Theoretically you should buy the pack last. I would say go ahead and get your pack. But limit it to 3200ci or less. This will work for you for all but extended trips. For more than a week, you want another pack. You will have two packs...so? One for trips up to a week, one for longer trips,ie, two and three weeks. The difference in weight between them will be quite a bit. Around 1pound-1#8 for the small one (handling loads up to 25 pounds,) and, 3#-5# for the larger one, handling loads between 30 and 50 pounds. If you are working, you may not get that much time off. Soo, go with the smaller one at first. The Circuit is 2#4. Trying to be both a light weight pack and a 30 pound weight lifter. Compromise never works as well as specifics.
Synthetic bags loose loft relatively quickly, especially if compressed. If you get one, DO NOT compress it, or, compress it only lightly. 3 or 4 to one by volume. It might last 5 years that way. Once will destroy the loft, loosing about 10F of warmth. And it is heavy at a bit over 4 pounds (4#3.) But the cost is about 15% of a good down bag. Cheap down bags are about the same as good synthetics. Look at Western Mountaineering, Feathered friends, Nanutuk, here in the states. Marmut SS bags are OK. All run about 350-400. All will last a lifetime. Figure out wich is worth it over a few years... Good down is far lighter. About 1/2 or somewhat less. My 0F bag weighs less than 3/4 of your proposed Slumberjack 20. And it is lifetime guaranteed. Your bag will be the single largest expense. If you cannot afford a good down bag, Go with a cheaper down bag. They are more compressable at least. These usually cost about $100. If you are broke, then by all means...go with the slumberjack, just assume you will replace it as soon as you can.
I like E+lights. At 3/4ounce, 24-45 hour run time, they are a good choice. Light and good enough light for young eyes. You do not need 60 lumens of beamed light that can let you see for 40 yards. At night, in the woods, you will get a lot of flash back ruining what remains of your night vision with larger lights. Cheap, they work pretty well. They are water proof down to about 10 feet, so rain isn't a problem as it is with a lot of smaller lights. They cost about $25. You can strip them by removing the strap and whistle/buckle, simply clipping them to your hat or on your pack strap for night walking. A spare set of batteries is recommended. A secondary light, like a little 15g impulse(lots of these out there, just make sure it is water proof) lets you work around camp. I clip this to my wrist with a hair tie. I never seem to loose it that way. ABout $10.
Stoves? A cheap homemade alcohol stove, aluminum foil wind screen and K-Mart grease pot works. About $10. I eat right out of the grease pot. Cutting the edging off the lid and clipping the nub off the handle saves a bit of weight. For another $35 you can order a special Caldera Cone for them, but specify one WITHOUT handle cutouts.
A ti spoon, about a table spoon, works. These are about $10. Ethanol and methanol are common fuels. Canisters are the most expensive. White Gas is about the cheapest to run.
A 9x11 tarp will be plenty big enough. Cost should be about $65. Or make your own for about $35. The screen tent should be two person to match your size spec. These run about $80. Again, you can also make your own for about half that.
Water bottles and fuel bottles are reused soda and gatoraid bottles.
Stakes are difficult. Ti stakes are expensive...about $2 each.
You need at least one dry bag for food. This keeps water out of your food. Bear line is 1.5mm line. Smaller cuts into tree bark. Larger is heavier than needed. A small #1 niteize biner works OK. About $10-$12.
Maps or GPS? Well, I prefer a compass and a map. Sometimes a GPS is nice, but generally, I have rarely found it necessary...once in 40 years we missed our mark by about 100ft... Anyway, Thompsons waterseal on paper works well. The little pliers makes a good tool kit...optional.
Lighter, soap, AquaMira, knife, pencil, some paper, a few fire starters, 2-3 bandaids, duct tape, tooth brush, batteries, etc, miscelaneous stuff goes into a small dity bag. This is usually expensive to buy. So, I would say about $30. No, toothpast is NOT necessary. For a few days, no problem.
Camp site selection, bear bag tree selection, general camping lore, well, that would take more words than I know, I'm afraid. Stay on hillocks, or slight mounds, generally. Stay off ridges, rather camp on the leeward side, below a ridge. Don't camp in valleys in colder weather. Use heat reflectors on your back, first. Choose a tree with strong branch, 16' high, 4' away and drop the bag 3'. Avoid eating in camp, unless it is an old, well used campsite. Don't walk on rattle snakes. Don't sleep on scorpions. Keep moving when confronted by bug clouds.
Well, it is a start anyway. Lots of people will disagree...mu opinion only.