trainee is indeed a bit low for "having done everything" - did you do all daily challenges?I finished all quests, I'm through and I'm still only in trainee league. Obviously something is quite wrong here. You should, at least, be in silver league when you got through the entire event. It's a big mistake if just only the users are awarded who use a lot of diamonds. And with all of it done and only ONE ingredient item left I only got two levels of the harvest barn. Obviously the balance of the event was faulty.
On regular worlds I would expect to end up in apprentice when everything was done and no diamonds were spend, but it always depends on the whole server - if everyone is active it depends on luck (who has the least amount of ingredients left and how many ingredients did you find in incidents)