When Judging a prospective Mage (or similar arcane) player character, I first discuss what sort of Mage the player has in mind. This informs my selection of the first spell in the Mage’s starting spell repertoire:
“A 1st level arcane spellcaster starts the game with a base of one 1st level spell in his repertoire. The Judge should select an appropriate spell for the arcane spellcaster to begin with.” (ACKS p. 67)
To the extent possible, I hope to avoid cookie-cutter Mages, and a Mage’s first spell selection can kick this off by choosing a spell best fitting the Mage. I choose the spell from those available in ACKS core, the Player’s Companion or even a unique spell I construct as needed. Any remaining spells are determined randomly among the ACKS core spells only. In my games, there is an implied spell rarity, wherein core spells are common (among spellcasters), Player’s Companion spells are uncommon and other spells are rare or unique.
The Mage’s starting spell repertoire complete, I next ensure the player is aware of ACKS spell signatures:
“While spells have general effects that are common to all who cast them, the specific sensory effects associated with the spell will vary from caster to caster. This specific sensory effect is known as the spell signature. A spellcaster should write a short description of the signature for each spell he can cast.” (ACKS p. 69)
Spell signatures are an important aspect to customizing a Mage. Finally, I will advise the player on Proficiency selections which may be appropriate for the Mage. Proficiencies are the capstone to customizing an ACKS Mage.
As the Mage advances, magical scrolls, a magical wand and/or a magical staff are items the Mage will hope to acquire. When a beginning player does not realize this, the Judge should direct the player to the related rules. When a Mage is not fortunate enough to acquire these items through adventure, the Mage can turn to crafting the items. Again, the Judge should direct the player to the related rules as needed.
A Mage with Alchemy selected three times can craft potions as an Alchemist as early as level 1. As an example, a Witch can brew potions at level 3, but is delayed in scribing scrolls until level 7. I mention these to demonstrate that the crafting level limits could be tweaked by the Judge: "Every campaign is a law unto itself." Note that the ACKS Magic Research throw table supports throws for levels 0 through 14. I would not change these values, directly. I might consider campaign-specific and situational modifiers.
For something more dangerous to those looking for a swifter path to power, perhaps the rules-as-written level limits are in fact traditional limits arising in a campaign world over time. In this case, magic research can be attempted below the recommended levels, but failure could be spectacular! The Judge might use or adapt the Player’s Companion Magical Experimentation mishap tables to this purpose. Researching spells, scribing magical scrolls, or brewing potions prior to the recommended level might risk a Minor Mishap. Crafting magic items prior to the recommended level might risk a Major Mishap. Learning and casting ritual arcane spells, crafting magical constructs, creating magical cross-breeds, or creating necromantic creatures prior to the recommended level might risk a Catastrophic Mishap. (In such a campaign world, adventurers of all levels might be hired to stop an individual engaged in such dangerous research.)
Although certainly not necessary, a Judge running a campaign in a nudge higher magic world might consider my campaign rules for ACKS Level 0 Spells and/or Differentiating Mages. I have found Level 0 Spells to be a flavorful, not unbalancing addition (when appropriate to the campaign tone.) Although I have not experienced issues with Differentiating Mages, it may be many years before I personally can experience each option from levels 1 to 14 with a variety of players. Any feedback is welcome.