Highly second everything footscrazy mentioned.
I'm currently in my third month of traveling through europe on my own, I'm posting this from Portugal off my phone.. I would highly recommend pursuing it; if you book into hostels you rarely get lonely, there's always other travelers, groups and solo that you will instantly click with because your both following the same goals.
I've kept it super flexible, I had a rough idea of where I wanted to go and the route I was going to take but most if the time I would pull out a map 2 or 3 days in advance and decide which city/country I would visit next.
Transport in Europe is also extremely easy to use and figure out, most countries have the English translation or the words themselves are similar enough to English that you can figure it out. Most countries also speak English as a second or third language, Spain can be a little tricky though as they don't speak much English as I found out

But it gives you an opportunity to learn some words in the native language.
I've been in both the winter and summer, as a solo traveller it's quite easy to get beds and public transport on late notice, but it does fill up considerably in July and August and I would recommend booking hostels a week or more in advance for popular destinations like Amsterdam, Paris and Berlin.
I packed extremely light, a 28L backpack to be exact, but I would probably recommend a 32-35L, I went a but nuts with minimal luggage

The main benefits are been able to check all your luggage in as carry on which makes flying much more stress free if you have connecting flights and also much easier to move between places.
Initially it feels daunting to travel on your own but once you get into the swing of moving around it feels like second nature, you forget your traveling after a while..
The only downside I would mention is after a while of traveling it can be exhausting to continuously meet new people and answer the same questions, and it can be hard to have downtime when there's 6-12 other people in your room.. But the pros totally outweigh the cons.
It's freedom at its greatest, enjoy!