My first official tournament was in November of last year. It was pretty big (though by Scotland's definition of big, you're looking at 40 people, max.) and everybody there was friendly and welcoming! I didn't go there with the expectation of winning anything, but I managed to get a few friendlies on the go with some professional players and I learned a whole lot from them. In short, it was a ton of fun! I won't lie, I was a nervous nelly. But the nerves calmed down as the day progressed.
My advice to you firstly is that you should go! There's nothing quite like being surrounded by people who likely share the same interests as you. It makes it easier to go up and talk to people you've never met before. I mean, you're all there for one thing, right? So use that as a starting point! Y'know, ask people who they main and suchlike!
Also try to remain calm during the first stock of your first fight. For me, the very beginning of that match was the most stressful. Figuring out someones style whom you've never met before is such an intense situation. It's not over if they get a stock off you and they're sitting at 45% or what-have-you. Don't despair! You can come back from that! Yeah!
And finally don't be afraid to ask for friendlies! Practise is good for everyone! Just pick a setup and if there are people playing, ask if you can get next game. In the meantime, watch them play out their matches. You might be facing them in the first round! Scan them for info on their playstyle!
-Ah ha! I have you now! Weak point at the back of the knee! HIYAAAH!! Watch 'em fold like a piece of paper!-
In the end I say go, because hopefully your first tournament will leave you hankering for more!
Hope this helped somehow. :^D
(Also, if you want some sparring practise I'm always down to clown!)