
NEMO
Disco 15 Series
Spacious for side sleepers; bulky, temp rating optimistic.
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I use a synthetic bag (20° Kelty Cosmic) and/or quilt (20° EE Apex) + a S2S Rector all the time and I think you’d be well served with a synthetic + fleece system. I would also look into a mega-comfy pad to put on top of the cot. Exped or Thermarest are my preferences there when weight/size doesn’t matter.
Apex from enlightened equipment, bring it up with their custom builder. You can spec the temp rating you actually want instead of guessing. Hammock Gear's Econ Burrow Synthetic is the cheaper version if EE's lead time is too long. Both will be lighter than your Night Cap and pack way smaller. Just be honest about your real low-temp expectations when you order.
Enlightened equipment. Chose your temperature, fill and size. They make wuits but the convert is awuilt with a zipper. My 20 deg bag weights 18 oz. I got the regular wide so it airy in the summer and i can wear a poofy wirth a hood when its ccols as i i like climbing mountains and backcountry skiing. I couldnt imagine a better bag. Been sleeping outside since 95.
I have the EE 20F enigma. It works well for southern utah. If you feel cold in it at low temps I recommend a bivy. It keeps drafts away and will keep you warm enough. Are you a cold sleeper? What’s the lowest temp you have used it in?
Those were just examples for the criteria I listed, which may not be your actual criteria. I actually have that sleeping bag and it's fine for a side sleeper. A bit tight, but still very comfortable. I just replaced it with an Enlightened Equipment Enigma 20 degree quilt in wide size. I was able to drop a pound off of my weight doing so. That's an expensive quilt though, especially in 950 fill. You may want a square sleeping bag, or wide quilt if you're an active sleeper. You don't have to buy an inflatable pad, but they sure are comfortable. I spent years on the trail waking up stiff. After buying an inflatable mattress and pillow, I wake up feeling good. You can also get a foam pad like the Nemo Switchback, which is a lot cheaper, but not as comfortable. Your ground mat (whatever style you choose) provides insulation between you and the ground. We lose a lot of heat through the ground without a pad. The insulation value of the ground pad will be rated with something called R value. Foam pads are usually 1-2 R value. The Neo Air I suggested has an R value of 4, which is approaching late fall, early winter levels of protection from the cold.
There are lots of good YouTube videos about “budget backpacking set ups,” like from Justin Outdoors. I would look at a different freestanding tent. There are budget options around the price of the tent you have here from semi-reputable brands like Naturehike. REI halfdome might be another good budget option especially on sale. Tents are tough because it’s hard to know what you’ll want out of an expensive, end game type tent. I think it’s very reasonable to get a cheap tent for your first time. Just make sure it’s reputable enough that it won’t be a total waste of money. And make sure you know what you’re getting between freestanding vs trekking pole tents. Naturehike also seems to make decent budget sleeping pad options (don’t trust their R Values though, get a warm one). The rei helix is a warm and high quality pad. Very comfortable too. Sometimes they go on sale for about $120. I have it and have zero regrets. Pillows can be had for quite cheap too. I would get one with a pad strap like the Enlightened Equipment Cloud 9 for $25. Not sure on budget sleeping bag options but if you can stretch to a synthetic Enlightened Equipment quilt for $230-$240 I think that would make a lot of sense. Even if you eventually upgrade to down, the synthetic quilt will still be useful if you’re going somewhere super wet. I would just skip the compass. Most people will just use navigation apps like onX on your phone (which you can probably just get a free trial for). Can’t go wrong with that sawyer filter, but you might want to consider the one with the larger 2L bag. It has a big opening on one side that makes getting water very easy. Good option especially if you’re not too worried about weight. A platypus QuickDraw with a cnoc 2L is a good option too. If you can handle the bad taste, iodine tablets could be a great way to save money here. Not sure on those gas canisters. I’d just get one from rei cause you know it can be trusted. It also won’t be too much more expensive and you can buy just one to save money. The brs 3000t and a toaks 750 ml pot is a great budget cook set for about the same price. Much lighter, also tried and true. If you’re going with friends you might be able to just use their stove too. Offer to carry their gas. Costco is a great option for bear spray. I believe it’s cheaper and I would trust it more. Costco trekking poles are also very popular and cheap. Don’t forget about food storage if you’re going into bear country. REI rents out bear canisters. Bear canisters are also important to keep critters away. Honestly, just skip the multitool altogether. If you must, get the smallest Swiss Army knife for not that much more. Skip the towel altogether too. If you must, a buff/neck tube will serve the same purpose (plus many more!) for about the same price. Skip the first aid kit too. Make your own with leukotape for blisters and some bandaids. You won’t need much more. Skip the wipes. Just use toilet paper to save money (please pack it out in a dog poop bag, especially if the area you’re going to requires it). A backcountry bidet would be about the same price and almost certainly lighter. Having a dialed in sleep system is the most important part, both for comfort and safety. Save money by just not buying the other stuff. Your first time should be relatively tame anyways so stay away from buying stuff just in case. You’ll learn what you need with experience and you’ll be able to make smart investments in higher quality stuff. Have fun out there!

NEMO
Disco 15 Series
Spacious for side sleepers; bulky, temp rating optimistic.
Hammock Gear
Classic Burrow 20°F
Budget king; very warm but heavier than ultralight.

NEMO
Disco 30
Spoon shape for side sleepers; prone to zipper issues.

Western Mountaineering
VersaLite
Durable, very warm; premium price, too hot in summer.

Katabatic Gear
Alsek 22°F Quilt
Versatile 3-season quilt; secure pad attachment, high price.

Ranked #1
NEMO - Disco 15 Series

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Kelty - Tru.Comfort Doublewide 20
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Enlightened Equipment - Revelation APEX

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NEMO - Disco 15 Series

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Feathered Friends - Egret UL 20/30

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NEMO - Disco 15 Series