make it 40+ or 52+ for a start, and dont give some sick rewards like epics, cause this is what destroyed EU classic.
Big chance for usefull rewards like fruits, buff scolls (at least 2nd class not useless 1st), potions, b soe, b res, xp boosts. With those rewards people are always happy. Dont give shit reards into pull because they only make people angry, but also dont give some end game items with chance that will flood server with free cloths etc. Also there was nice event on EU classic with colletcing letters - decent rewards for certain words. People like to collect things, give it to them
This is classic, it should be HARD. GMs gave epics level 3 and weapons B/A+16 on EU classic and people mass quit because of that. All the fun is to chase the rabbit, not get one for free, doing nothing.