Um *scratches neck* I would suggest you experiment a little and figure out for yourself what makes you the biggest profit, I personally level up to 7, but I've seen people level theirs up to 10 or 12.
Also, Idk if you saw Silverwind's reblog but:
I tend to average about 50k a day just from familiars/chests, Crim, and occasional dragon sales/level+exalting. If I have more time to grind the coli or the fairgrounds, I can easily double that in a couple hours. I get occasional windfalls from selling expensive items or dragons, but for the most part I’m not using any amazing secrets, just selling food in the AH (seafood’s always in demand, I tend to charge 75-80t a food point and people seem to be happy to pay), bonding familiars, and exalting dragons.
Good comment. I totally forgot about familiar bonding and Crim, lol it's become so routine. You can make make SERIOUS BANK off familiars.