I (mid 20s M) just came back from a one bagging trip where I mostly stayed at hostels. I've always traveled with an ordinary pack, but it's the first time I did research and bought items to make the trip easier on myself.

Here's what I took with me:

• Bags:
  • Mystery ranch Scree 32L
  • Quecha NH100 10L pack (as day pack)
  • Sling (only used when I didn't/couldn't have my passport stored in a secure place)
• Clothing:
  • 7 t-shirts
  • 7 pairs of underwear
  • 7 pairs of socks
  • 1 pair of jeans & belt 1 pair of hiking pants
  • swimsuit
  • shorts
  • 1 thin long sleeve shirt
  • winter jacket
  • buff
  • ^\) hat
• Toiletries cleaning
  • Decathlon pool patch to hold everything I'd need for showering liquids you need to take out at the airport
  • Lush shampoo bar Matador FlatPack soap bar case
  • Hair brush (broke off the handle to take less space)
  • ^\) 3 tiny containers for body wash, conditioner & lotion
  • toothbrush floss 2 small travel sized toothpastes --> only used 1
  • Beard Trimmer 3 guides usb cord for charging (used the trimmer, but didn't have to charge it, the battery lasts for far more than 3 uses)
  • Nail clippers ^\) tweezers
  • ^\) Large micro fiber towel
  • ^\) 1 Laundry tablet 2 dryer sheets
  • Deodorant
• Medicine first aid
  • Vitamin C & D
  • ^\) Advil & Tylenol
  • ^\) Imodium
  • 2 bars of halls --> used both, but half of one would've been enough
  • polysporin (used) ^\) another medical ointment
  • Medical tape
  • 2 small containers of hand sanitizer --> only used 1
  • 2 already used packs of anti-bacterial wipes (1 brand new would've been enough) bunch of random single packs
• Miscellaneous
  • 1 pair of trail running shoes
  • pair of slippers plastic bag to carry them in
  • 3 medium packing cubes:
    • 1 that has 2 sides: for underwear socks
    • 1 that has 2 sides: for t-shirts dirty clothes
    • 1 with 1 zipper used for Miscellaneous items like the long sleeve shirt, shorts, towel, souvenirs, etc
  • ^\) 4 pieces of Velcro 4 zip ties 2 carabiners hair ties (never really used any, they were there in case I needed some in a pinch)
  • ^\) tenacious tape
  • Number of zip lock bags (maybe only used 1) a plastic bag
  • 20 or so masks --> didn't use all
  • a lock keys
  • Passport printed documents
  • Phone charging cables charger adapter
  • 2 wired earphones (my day to day was about to die, so brought a new pair too, but never used the new pair
  • ^\) power bank
  • sun glasses
  • ^\) very small notebook pen (ended up writing notes on my phone instead)
  • head lamp --> used the red light 3 times, but didn't think I was ever gonna use it
  • ear plugs
  • Wallet
  • Book --> wanted to exchange it once I finished it, but didn't find anything not bulky and interesting in a language I can read
  • Snacks gum
  • gifts for friends
  • EDIT: half a liter metal water bottle
• Stuff purchased on the trip:
  • Souvenirs snacks
  • Another set of lock keys
  • charging cable (lost the adapter for the charger I brought)
  • slippers (forgot my original pair at a hostel)
  • Vaseline Moisturize
  • EDIT: Also always kept a plastic drink bottle as a second water bottle

^{Any item with \} indicates it not getting used the entire trip.)

Notes on the above list:

• I didn't have my day pack in the big pack ever, mainly because there was always some very crushable food in my back so didn't wanna fill it to the absolute brim. But I suspect I could if I wanted to, except on the way back, I filled up the pack almost to the limit with chocolate and other snacks. If I had my pack on, the day back was small enough to hold in hands, or attach to the hip belt. For that reason the title says 32 L.
• This is the first time I take a day pack instead of a random drawstring. At the cost of $5, I definitely take it over a drawstring.
• First thing I have to say is that a backpack designed for carrying load made a HUGE difference. Didn't experience any back, shoulder or neck pain due to carrying my backpack for the first time traveling. I highly recommend packs with a hip belt for any traveler. Everyone has different taste and requirements for backpacks so I can't recommend any packs, but I know I'll only ever get those with good hip belts for traveling and hiking from now on.
• Luckily I didn't get sick during this trip, so aside from the vitamins (which I didn't even take half of), thankfully none of the pills got used. Specially happy I didn't have to use Imodium this time around.
• A lot of places you stay at give you shampoo and body wash, so there was no point to bring extra containers on top of my shampoo bar, as the bar alone would've covered me alone the entire trip.
• Speaking of shampoo bar, it quickly started to disintegrate and had to paste it all back together a few times. I found it works the best if I dry and wrap it in toilet paper after use, but I couldn't always do so at hostels.
• The patch I used for the toiletries worked beautifully. It was an idea I got from this sub, thanks guys.
• I used hostel towels all the time. The one I brought with was to be used as an absolute last resort. I have come to learn I don't enjoy carrying a wet or damp towel in my pack, so it's the only item that I took with and purposefully didn't use. The prior 2 trips I didn't even take a towel with me.
• I brought laundry stuff, but ended up doing so at a friend's so didn't use the tablet or the sheets. One of the sheets was meant to be placed with dirty clothes to damper the smell, but totally forgot to do so. Woops!
• I didn't have to bring my beard trimmer, as I can go months without shaving. But I also wanted to use this trip as trial for longer traveling. So I brought the trimmer, the towel, and couple of other things just to see how a months long trip in my pack would be like in terms of weight and volume. At this point, the only thing missing from a longer trip is a laptop.

General comments:

• Clothing (t-shirts, socks & underwear) were brought in 7s, so I didn't have to think too much about how many days they'll last, or in how many more days I needed to do laundry. So for example, if I were to wear everything for 1.5 days on average, then every 1.5 weeks I'd have to do laundry. I found that handy in the first half of the trip, before I did laundry, but afterwards, I never thought about it again.
• Can't say enough good things about Merino Wool. This is the first time I used merino for traveling.
  • 2 of the t-shirts were merino and I easily wore them 3 or 4 days before washing. I didn't go more than 2 with the other t-shirts, simply because they started to smell more than I liked.
  • The long sleeve was also merino, I used it for hiking on top of a merino tshirt. It's very thin and isn't meant for warmth, but I was fine wearing it in single digits.
  • I brought 2 pairs of long cut merino socks 1 pair of short cut wool socks. Also wore them 2x or longer than the usual socks.
  • I'll definitely pick up more merino or wool in general for the next long trips, so I can take less with me. Merino isn't cheap, so only buy if it works for you. I wouldn't buy bunch at once, rather look around for sales.
• I bought the hiking pants since it'd be nice to have a second pair of pants and they could be unzipped to become shorts, but I never used them as shorts. They can also be used as swimsuit (based on the material), but I'd need a belt or else they'll come off the very first dive since they're a little too big. I only used the hiking pants the couple of times I hiked. They got very muddy and worked better than my jeans, but I don't know if I'll take them again if I only use them for hiking. I'd like to not take 1 of the following next trip: second pair of pants, shorts, swimsuit. So either gotta find shorts I can go in water and dry quick, or get a good water proof belt for these pants, or something else. I rather have basketball shorts to chill in, than these hiking pants.
• I can handle cold so I was OK with only t-shirts. And I don't care much about how I look since I'm not particularly attractive, so ordinary t-shirts and a pair of jeans work for me (perhaps a reason why I'm not attractive lol). I totally understand if that won't work for you in terms of warmth and looks. I do recommend you taking warm clothes in winter, it's unnecessary for me.
• You can buy things from where you travel to, so no need to bring everything with you from home. There are stores and pharmacies everywhere, unless you're specifically going to the nature. So I could've brought less toothpaste, vitamins, pills, bandages, even clothing than I did.
• Weather was always in single digits celsius, it rained many days, but it was mostly cloudy. My jacket wasn't meant for rain, but rather snow. I did feel a bit wet number of days were it rained all day. Ideally I should ditch that bulky jacket for a combination of wind breakers and rain jackets. Any suggestions?
• I will travel with 2 locks from now on. One to lock your stuff in hostel, another in case you need to lock your phone an wallet if you're out (like going swimming, etc). But carrying the keys becomes a hassle, so perhaps keyless locks.
• Traveling in hostels means there's always a loud snorer. So when that happens I listen to music while I sleep, it works better than ear plugs for me since instead of just blocking the snore, you block and add extra pleasant noise on top. My phone has a radio receiver, so I connect to a local FM channel and so don't have to listen to the same songs all over every night, and it uses little battery to do so.
• Definitely leave empty space in your bag for souvenirs, gifts, local food or drinks, etc. it's worth it.
• Please be considerate of others in hostels, this includes myself. If you have to leave early in the morning, pack in the evening if possible. I'm prob gonna sleep with my bag from now on when I have to leave early morning. I made more noise than I liked getting my bag out of the tiny box under the bed and doing the final packing (toothbrush, charger, slippers, etc) on my top bunk. And for the love of god don't turn on the lights when everyone is sleeping. Either pack before bed, use your phone's flashlight, or get a headlamp with red light.
• I enjoyed using the buff. I used it as neck warmer, headband, and hat. It didn't do any of those jobs excellently, but just good enough.
• Only started getting blisters on the last week of the trip, the trail runners worked great.
• Always bring swimsuit with you traveling.
• Don't forget to enjoy yourself and have fun when traveling. It might mean you have to spend more money than you'd like once in a while, or throw some stuff away, or take rest days to recover.