I've been to cons when they just started up, and to cons who have been big from the start (for me). I've also been to cons which have grown over the years. It used to be anime cons. I also once went to a Minecraft con because a friend asked me to
Now I just go to furry cons
I can't really answer what con would be a good place to start for you personally. If you've never been to one, I think a small one would be a great idea. It's a great way to start orientating how a con is possibly built-up and what kind of events/workshops/panels there can be.
If you want to go to a pretty large UK con (and one of the two largest ones in Europe, if I recall what Uncle Kage and others have said, as well as the amount of people attending), I would suggest Confuzzled. That's mostly because I've had personal experience with that UK furry convention, and people have been rather nice there (and the staff helpful
).
As of which, you say abroad, but I only know of USA furry cons and one other European country (Germany) who has bigger furry cons, but I can assure you Confuzzled is catching up immensely quick on those USA cons with amount of people attending
You can check out Confuzzled's website:
https://2017.confuzzled.org.uk/ And read up on all kinds of information there. Maybe that too will help with your decision.
All in all, whether going to a small or a big con, if you like cons, people, fursuits, events, etc, it doesn't matter the size
Hope this helps~