What's the *best* beginner backpacking gear for Scouts?
Best = cheap, new, easily obtained, only starter quality, and pretty much works. This .com if full of optimized, $3000 opinions — I'm cheap. Buying used and borrowing gear is ALWAYS your best bet, but if you can't read on.
Below is for the new Scout (parent) who's reluctant to spend even $100 (as I was as a boy and am now w/ my kids). Its fully expected a few Scouts will stick with backpacking and buy far better gear someday, but to start 'go cheap'. Its also assumed boys have good teachers/guides as to mitigate the shortfalls of weight/quality.
Top 4 places to buy: Walmart, Aliexpress (cheapest but slow), Sierra Trading Post (wide variation), and Google Shopping (great for those 90% off, one-size left things if you can precisely name what you want).
Sleeping Bag
You can't beat Walmart's Everest mummy for $24 — 5 F rated (20-40 F realistic per reviews), 3.5 lbs,, polyester. Reviews show it fits both boys and 277 lbs adults. Yes, its overkill for most summer jaunts, but still best if you can buy only one. Remember, boys should learn to wear almost all of their warm clothes when inside bag (for cold nights).
Sleeping pads (plural)
Again Walmart's blue or green foam 0.5 inch thick pads. For spring & fall, you'll need 2 layers (either 2 pads or one folded in half for short kids). For winter, even 3-4 layers will mean more heat lost below than above with the above bag. Later boys can learn to trim to torso length, use a pack under the feet, etc. $20
Stove & mess kit
See my other post on pop can + tomato paste can + windscreen + fuel tablet stove. Add a cheapo spoon and eat from Ziplocks. $2
Backpack
In general, both should be smaller than an adult would use, especially the pack b/c most Scout think they need to fill it up. Look for a 30-50 liter pack (my 10-yr-old's 30L fits everything inside, not strapped on). $9-$50/pack.
Maybe Tent
Only one-third of Scouts needs a 3 person tent so buddy up. Make sure the rain fly fully covers the tent (no little hat rainflies). $50-$100. If you can teach boys lightweight very well, the tarp + bug headnet + hiking pole is a lighter, cheaper way to go. $60. Groundcloth for both = shrink film plastic for windows, outdoor strength (aka polycro, but not for deserts) $10
First Aid Kit
Ziplock w/ fabric bandaids, small Neosporin tube, and couple handiwipes / wet towelettes. Larger patrol kit should cover all else. Many hospitals give out free mini-kits for marketing, call around. $2
Raingear
Lightweight umbrella = the driest Scout in the Troop after a full day of rain on the trail. Secondly for both warmth and rain, get a waterproof (not breathable) and fabric (not plastic) shell/jacket/raincoat. Walmart's Coleman rain parka $30. AliExpress "waterproof jacket" $9. Odds are high of a good find at Goodwill / Salvation Army / thrift shops.
Clothes
Polyester long underwear top + bottom, 3 pair wool socks (1 worn), nylon wind/trail shirt & pants, warm hat, ball cap, ugly poly or wool sweater. These are essential. Remember "cotton kills". Again Walmart.
Storage
Waterproof Everything!. Forget nylon stuff sacks. Use freezer Ziplocks bags inside cheap grocery store bags to organize items. Use a trash compactor plastic bag as a packliner, plus a spare. (Normal lawn bags ok too, but thinner & bigger.)
Shoes / Boots
Sorry, I don't have a *best*. I tell my boys to go with what they have that's comfortable and pack 2 pairs wool socks. If pack weight is kept low for hikes in summer/fall, normal shoes are fine.
Misc.
LED keychain-type flashlight or headlamp – http://www.ledshoppe.com. Any Bic lighter. One or two 1 liter soda bottles for canteen. Any plastic whistle (think toy). Handsoap in Ziplock. Toothbrush & paste in Ziplock. Plastic playing cards deck (one per pair of Scouts). Simple 3" lockblade knife.
Food, Drink tips
Snickers or another peanut-candy-bar for late morning and afternoon snack on the trail – just as good & cheaper than energy bars, less messy than gorp, and boys like them more. Single-use powdered juice tubes (not sugar free) to pour into canteen. Both needed to keep boys spirits up while walking.
Result — Gear for an overnight or a whole week for $200 (and likely far less since its likely many households have most of this stuff).
Remember — max a boy should carry is 20% of his body weight… thus many boys' packs before adding food & water & patrol gear should be only 10-20 lbs.

