I dunno. Getting rid of disease seems like the best thing to start with. And making enough food and shelter and basic necessities for everyone. Magically fixing the ozone, saving the whales, etc. etc. Basically, I'd do all the unquestionably good things the world needs. After that, I guess I'd take petitions from people for other changes they'd like to see. 'Cause, you know, I might think it sucks to live with Asperger's, but maybe someone who has it thinks it's part of who they are and doesn't want that to change. So I'd wait to hear from anyone who has it and wants it gone before taking it away.
And, ya know, with all the people surviving and people being what they are, I'd make a couple of extra Earths so people who don't want to live together don't have to.
It would all manifest with pink sparkles.