I just went to my first Esperanto congress, the IJK in Poland, this year. I had a great experience, especially meeting everyone I had been getting to know over Telegram. Is there a congress you'd especially recommend for beginners my age (20-30)? Is that the IJK or something else?
There is Somera Esperanto Studado particularly interesting for beginners, as it has a focus on learning, courses in the morning, other stuff in the afternoon and evening.
Further more I'd recommend to people in their twenties to check out the two summer meetings FESTO and IJS as well as the winter meeting JES
Note that these are all European ones. I am not that well informed about meetings in other continents.
Contrary to what happen in most conventions and many meetings of Esperanto-speakers, I do not recommend to study Esperanto at these places. Esperanto should be learned at home or in a class. Even going to class, most learning should be done at home.
Esperanto meetings or conventions provide a good opportunity to USE Esperanto. If you are in class, you will miss this opportunity. You will get fluent faster using Esperanto than studying Esperanto. But make sure that you learn/study Esperanto at home.
There is a permanent list of Esperanto events in this page: