How does leveling up a spellcaster after a prestige class that advanced spellcasting ability work?

Question

I am playing Pathfinder and interested in taking the Dragon Disciple (DD) prestige class for my Sorcerer (with a draconic bloodline). I understand that as the DD levels up, the spellcasting abilities level up but not the actual Sorcerer level.

When I am, say, a level 5 Sorcerer and level 8 DD (with the casting ability of a 13th-level sorcerer), how does the leveling up of the Sorcerer progress from there? Do I level up my Sorcerer and make the jump to level 14? Or do I level the Sorcerer up to level 6, and only get the ability modifiers but no advancement in spells?

And, if there is a jump to level 14, do I get all of the ability modifiers (attack, saves, etc) from all the middle levels as well, or just from level 13-14?

Answer 1

It works exactly the same as with any other multiclass character. In your case, your Sorcerer level will increase to 6 and you will gain all the features that a Sorcerer would normally gain when advancing to that level.

The advanced spellcasting ability of the prestige class (in this case Dragon Disciple) increases your effective Sorcerer level for the purpose of determining your spells per day (and, because a Sorcerer is a spontaneous caster, your spells known). It is simply a number that you add to your actual arcane spellcasting class level (in your case Sorcerer) to determine your effective level.

From the d20PFSRD for the Dragon Disciple, the FAQ/Errata box mentions:

The increase to his spellcasting level does not grant any other benefits, except for spells per day, spells known (for spontaneous casters), and an increase to his overall caster level.

In your particular case, as a Sorcerer 5/Dragon Disciple 8 you will have an effective Sorcerer caster level of 11 (5 from your levels as a Sorcerer and +6 from the Dragon Disciple's Spells per Day class feature).

At this point you will have the following Spells per Day and Known Spells:

        lvl   1 2 3 4 5

per Day 11th  6 6 6 6 4
Known   11th  5 5 4 3 2

When you advance to Sorcerer 6 you gain all the benefits that a level 6 Sorcerer would normally receive, however, because of your Dragon Disciple levels your effective level for the purposes of Spells per Day and Known Spells will be 12.

        lvl   1 2 3 4 5 6

per Day 12th  6 6 6 6 5 3
Known   12th  5 5 4 3 2 1

Answer 2

Dragon Disciple says:

At the indicated levels, a dragon disciple gains new spells per day as if he had also gained a level in an arcane spellcasting class he belonged to before adding the prestige class.
He does not, however, gain other benefits a character of that class would have gained, except for additional spells per day, spells known (if he is a spontaneous spellcaster), and an increased effective level of spellcasting.

So, you get the spellcasting of a 14th level sorcerer, but all other abilities of a 6th level sorcerer.

Another way to look at it, is to count all your sorcerer levels first (whether you got them before or after the PrC).
Take all abilities of this level of sorcerer. Then add the spellcasting levels (and other abilities) granted by the PrC.