Leaving Evermeet Isle (League Side) is a simple matter of doing the World Mystery quest chain. (The ones with the sun icon floating over the NPC heads). You can leave "early" if you like, but you really should be at least level 6.

Once you've left, you can't go back, but the only things there basically amount to better gear before you reach level10, when you can get Novograd Construction Council gear and dispose of your Survivors gear. And it really doesn't take all that long to get to 10, plus all the quests you'll be doing to get to 10 give you better gear anyway.

But staying and doing most, or all, of the quests on Evermeet gets you used to combat on weaker monsters in Allods, you'll deal with a few "boss" monsters, and so on. And with the current massive population boom, staying in the crowded Allod gives you organizational and social skill training.

Rep gear on League or Empire is never Needed but it helps alot and if something should become a bit hard it'll come back to bite you on the rear as you say "MAN I shoulda got the rep gear"Besides the farther you go in game the more the Rep gear will help you GREATLY and Allods Gold Not having it will be a bit of a hindrance.

The pain of being level 5 in light wood, is you can run out of quest quick. Also just having survivor gear you get from Clement's tower is not very good for Lightwood. The Rep gear helps but not a necessity, it is recommended to get that before leaving Evermeet. Then there is the new bugs making it tougher.