Here are some solid recommendations from Amazon:
Tent - https://www.amazon.com/Big-Agnes-Copper-mtnGLO-Backpacking/dp/B08175NX4C/
Backpack (mens) - https://www.amazon.com/Osprey-Packs-Atmos-Backpack-Abyss/dp/B077H3G5J4/
Backpack (womens) - https://www.amazon.com/Osprey-Womens-Backpacking-Aurora-Purple/dp/B07GHKJSWD/
Sleeping bag (mens) - https://www.amazon.com/Big-Agnes-DownTek-Sleeping-Regular/dp/B07M9WL54C
Sleeping bag (womens) - https://www.amazon.com/Big-Agnes-DownTek-Sleeping-Regular/dp/B07MH3B1R2/
Sleeping pad - https://www.amazon.com/Therm-Rest-Ultralight-Backpacking-Mattress/dp/B07YFXVVFD
Pillow - https://www.amazon.com/NEMO-Nemo-Fillo-Goodnight-Gray/dp/B083BJH5NX/
Stove - https://www.amazon.com/MSR-PocketRocket-Ultralight-Backpacking-Camping/dp/B07L5S65HR/
Pot - https://www.amazon.com/Snow-Peak-Trek-Aluminum-Cooker/dp/B000AR2N2Q/
Cup - https://www.amazon.com/Snow-Peak-Single-Fresh-Water/dp/B004YOMW40/
Bear can - https://www.amazon.com/BearVault-Resistant-Canister-Backpackers-BV450/dp/B001V9HENU/
Water filter - https://www.amazon.com/Sawyer-Products-SP129-Filtration-Squeezable/dp/B00B1OSU4W
Water bladder - https://www.amazon.com/Cnoc-Outdoors-Container-Thread-Orange/dp/B07QBQ894L/
Headlamp - https://www.amazon.com/Black-Diamond-Sprint225-Headlamp-Ultra/dp/B081B8CXH6
Satellite communicator - https://www.amazon.com/Garmin-Lightweight-Satellite-Communicator-Handheld/dp/B09PSSSFPF
Knife - https://www.amazon.com/Victorinox-Swiss-Classic-Pocket-Knife/dp/B00004YVB2/
Dry bag - https://www.amazon.com/Sea-Summit-Lightweight-Sack-Large-13-Liter/dp/B001Q3KKG4/
First aid kit - https://www.amazon.com/Adventure-Medical-Kits-Ultralight-Watertight/dp/B0009RIQBE/
Chair - https://www.amazon.com/Big-Agnes-HCHAIRONEB-Helinox-Portable/dp/B007ZGOWZQ
If you don't like those specific items - the brands are all legit, see what other options they offer.
REI.com has a list/registry option too. I recommend it over Amazon - where questionable products are abundant.
Clothes are hard to buy as gifts - but important for backpacking. Patagonia, Arc'teryx, Icebreaker, Darn Tough, and Smartwool make quality stuff.
You could also add a bunch of fancy dehydrated meals like Mountain House, Backpackers Pantry, and Packit Gourmet. Or just flats of beef jerky and dark chocolate.
Got it.
The filter I pour it through is for making unknown water potable (for backpackers and such):
I have it hanging like a separatory funnel and use gravity to filter the water. It has an extremely high flow rate and lasts forever with regular backwashing. This seems extraordinary to me because a vacuum flask with suction and a buchner funnel with 11micron paper takes orders of magnitude longer. This is one of the things I want to check.
Any thoughts on this device?
Big 4 for $502
The rest of the gear is relatively cheap, like:
Random stuff from your house / DIY:
Clothes could be a whole post of their own. Start with what you already own and upgrade to wool/synthetics over time.
Food from the grocery store is cheap. Skip the fancy freeze dried stuff. Shout out /r/trailmeals.
Skipping unnecessary items is the best way to save money. Amazon will make you think that a huge knife, lantern, chair, axesaw, and other 'camping' gear is important. Don't let them trick you into wasting money / weight on garbage.
EDIT: added a few items