It’s never too early! Maybe make reservations now for the parks in the order that you think you will want just to secure reservations, then change them if necessary once you make your ADRs. You’d hate to get locked out of any park.
If you really don’t want to make reservations now make sure to keep a close eye out on reservations in the weeks/months coming up on your trip so that if it looks like a certain park is getting full you can jump on it.