How I play it is that Dragons still get the arcane and divine spells by monster class by however it states in the Monster Manual. Being an advanced and intelligent race, dragons can learn and take on character classes that would stack with their monster class as well. Such varieties would invariably increase dramatically in CR and personal power as time goes but at greater cost and sacrifice. A Red Dragon, very old, who has 15 levels of Cleric and 10 levels of Wizard on top of his monster class, will be poor in terms of money, treasure and possibly even influence in the lands. This would reflect the many years he spent studying as a mage and cleric thus neglecting the typical red dragon behavior of collecting treasure, expanding their territory and increasing their perceived worldly power.
(13th level sorc I believe correct?)
