Earplugs. Usually, when you stay in a hostel, you are sharing one room with many beds with many different people. These people are all coming into bed at different times, many of them have been partying all night, which means a lot of stumbling around and searching through their bags. Then in the morning, people are all going to be waking up and getting ready at different times. It’s going to be noisy, and earplugs are a total life saver if you expect to get any sleep.
A towel. Many hostels will have you bring your own towel. Some hostels (mainly in Europe) may have towels for rent during your stay, but if they don’t offer this service and you didn’t bring one, you might be out of luck. Sometimes, it’s also good to have as an extra blanket on hand in case your bed not warm enough, or even clean enough, for you.
A refillable water bottle. For developing countries, this is always a must. Depending on the places you go, it might be better to invest in a filtered refillable water bottle. When I was in Bali, even just a mouthful of their tap water could make you violently sick. Instead of constantly buying water bottles, I had my filtered water bottle with me and it worked flawlessly. Worst case scenario, I could fill it up in the sink if I was really thirsty, but many hostels had a water bottle refilling station.
A padlock. Sharing a common room can have its cons. Traveling with cash, tech, and other valuables is pretty much unavoidable, but preventing them from being stolen is avoidable. Most hostels have lockers for you to put your stuff in, but they usually don’t supply you with a lock. It’s always good to have a lock with you not only for hostels but in airports. You can lock your zippers together so no one can reach into your bag and steal anything.
Shower socks. Common bedroom, common area, common bathroom. You never know who has been in the shower before you and how often they get cleaned. Keeping your feet in shower socks can prevent fungus and infections from happening.
All of this being said, I am a huge fan of staying in hostels. You get to meet loads of different people from all over the world, and you all have one thing in common, you love to travel. I’ve gone to dinner, bars, and even some landmarks with people I’ve met in hostels. It’s a friendly, open-minded community of people, plus it’s cheap. I would stay in hostels in Indonesia for $10 or less a night. Having these essentials takes out worry and can help your stay be a lot more pleasant.