Backpacking trips should be fun, and no matter where you travel around Europe—or anywhere else for that matter—traveling light is your best bet for maximum enjoyment. Nobody wants to be exhausted after a short walk from the train station to the hostel. I've probably seen that exact scenario thousands of times in my travels. A couple of years ago, I spent just over two months backpacking through Spain, Italy, Greece and Germany with a 25-liter pack.
Unless you're trying to spend your trip with near constant back pain, a relatively small backpack is definitely the way to go. With that disclaimer in mind, here are some must-haves for your first backpacking trip across Europe:
As a photographer, I lugged my fairly clunky Nikon D750 on my first backpacking trip abroad. But for most people, a small point-and-shoot or a good phone will do the trick. I mean, who doesn't want a picture of themselves holding up the Leaning Tower of Pisa, right? If you'd like to document your travels with the written word, tossing in a pen and small notebook would be another good thing to bring along.
If you're going to charge that camera or other devices, you're very likely going to need to get an inexpensive adapter. Unless you're staying in posh, Americanized hotels, you'll find the circular two-pronged plugs across Europe. It's best if you toss an adapter in your bag before scrambling to find one. All those helpful devices are useless if they have drained batteries.
A great way to ruin a trip is to fly into Finland without your passport. Don't be stuck at an airport waiting for your passport to arrive. Seriously, triple check that you have it. While you're at it, print out a copy of your passport to keep in your wallet in the event it gets lost or stolen. Or have a PDF copy on your phone. Every step you can take to safeguard yourself is worth it.
Again, it kind of goes without saying that you should have a few dollars saved up aside from purchasing your flight tickets. But make sure to have a small budget for unexpected museum tours, drinks at the bar or whatever your heart desires. Oh, and be sure to tell your bank and/or credit card company that you're leaving the country so they don't block any attempted purchases. Keeping cash in your pocket could also save you when you're in a pinch.
Clothes and Shoes
Clothes are why people end up getting those ridiculously large backpacks. You don't need a different T-shirt and pair of underwear for every day you're gone. If you think you do, I'd suggest budgeting a little extra, buying some clothes while you're abroad and donating or gifting them when you're done with them. Most importantly, pack what you think you'll need and then take less. Do you really need that dress or fancy shirt for clubbing? Maybe if that's something you do all the time. If not, that should probably be something you buy locally—wherever you may be—and leave for someone else. Same goes for shoes. Make sure you have something comfortable for everyday use!
Instead of buying a plastic water bottle, bring a reusable one. Aside from being environmentally friendly, this item won't likely take up any interior backpack space, as many bags offer exterior storage for such an item. Plus, you'll want to remember to stay hydrated as you walk city streets day after day.
The Right Apps
It's frustrating going somewhere in the 21st century without Wi-Fi. If you're traveling through more remote parts of Europe, I highly recommend the Maps.me app, which allows you to download area maps and use them offline. Take a look at other phone apps that might be helpful to you, such as a currency converter and translator.