While there is a LOT of good advice here, I’m just going to chip in with something else.
You may have produced a character with all the stats, and you may have worked out an interesting backstory (if it has a good story you can tell folk, so much the better). But what do you, or to be precise, your character, WANT?
What is their ambition, what is their drive, their goal? What do they want to do that can be accomplished during the event? For preference, something that doesn’t need much in the way of mechanical skills, but which does need a good amount of talking to people.
Examples:
(my first character) Record the symbol/heraldry/insignia/colours of every group on the field. This took me to absolutely everywhere, people were interested, I met lots of folk, and I sold a couple of copies of the results.
(my second character) Organise as many people as possible to do something in downtime. This meant finding the right people, telling them stirring speeches, and persuading them to join me in a mass sea-raid on the Jotun capital. Great fun.
See if you can become the expert in something. Maybe someone else knows about it, and you can ask everything of them?
Any crafting skills? Make something vaguely useful/interesting and try to sell it. Maps, artwork, props, food!
Anything that requires you to go and bounce off people (metaphorically) in an interesting way. Please bear in mind that while you could claim to be the Imperial Auditor of Facial Hair, and go around measuring beards, impersonating an imperial office could get you in trouble, so make it official. 