Failure means the spellcrafter must start over. Caretaker spells are created the same way. The main difference between the orders is the disposition of the spirits being petitioned. Caretakers interact with ancestors and family members who have died and been shown the proper respect. For example, places like concentration camps or mass graves are powerful places for Necromancers.
Most spells are focused to reduce their casting cost.
But there are some that can be cast with only a word or gesture. These types of spells, the instant, are generally underpowered because of the shorter available petitioning time. This makes the use of dusts, potions, elixirs, and staves more common than the instant spell. This is risky as any failure results in the spell's loss. If you playtest this, I would be interested in hearing how it goes.