[忍]

With the 10 spells from priority A, do you only gain 2 spells out of chargen from Dedicated spellslinger due to the Max number of spells being twice your magic? Does the mastery circumvent that?

[ShadowcatX]

Mastery does not circumvent that. That makes it a pretty bad combo with Magic A unless you have another use for spells. (Some GMs allow spells to buy PP on a mystic Adept.)

[Kiirnodel]

You could use the 10 spells from Magic Priority A to learn rituals and/or preparations.

[忍]

That's true +1

[Marcus]

Isn't there also a karma back per spell cashed in discussed somewhere in FA?

[Kiirnodel]

Only if you spend it on the mastery qualities.

Not really a karma back, but you can trade in priority spells for 5 karma each, but they only work toward the mastery qualities.

[UnLimiTeD]

You could, however, just leave 5 Karma for post character generation, and pick the quality then.
Mastery Qualities don't grow more expensive.
Difficult choice on Karma Gen, btw; Sure you get more spells that way, but you'd also pay 10 more for the first 10.

[Jack_Spade]

Yeah, that's probably the best solution. Otherwise you could argue that "specific trumps general" and just allow more spells on the character from the get go - it's called dedicated spellslinger after all, so you'd expect them to have a few more spells to sling than any other normal mage.