MM is going to be your strongest champ .. he will carry you through all content and progress your account the most. However, you still need a damage dealer, and since Kael will probably be in your CB comp for sometime until you find a better poisoner, and having one of the best AOE multipliers in the game, you might want to max him out first. Tayrel can also be used as a damage dealer, with more utility than Kael providing ATK down DEF down, stuns, TM decreases..
Rector is a strong reviver but seeing as how you just started this account, a reviver isnt going to be useful until later on in the game since you dont have any champions that are built yet to reviver in the first place.