It seems like there's some confusion about how spells work, so I'm going to try an assemble a primer here.
Determining the Spell and Casting Pool
Figure out what spell you want to cast, and any inherent modifiers specific to that spell. You can cast any spell if you have the Arcana level, but if your character knows the Rote, you can use the Rote dice pool; otherwise, it's Improvised and the dice pool is Arcana + Gnosis.
- Every spell is made up of what are called 'Spell Factors'. Beyond the 'effect' of the spell, these determine how powerful it is, how long it lasts, how many (or size) of targets are effected, etc.
- Every Spell must have a Potency factor of at least 1. If Potency is 0, the spell doesn't have any 'power' behind it and dissipates. Potency is usually, but not always, the number of successes rolled on the dice pool.
Typically you roll the dice and your successes are the power/effect/Potency of the spell, unless...
You can choose to adjust the other Factors of a spell:
- Target Factors increase the number of affected targets beyond the typical base of 1
- Size Factors increase the size beyond the typical base of 5
- Area Factors increase the radius of an area spell
- Volume Factors increase the mass/volume of a volume spell
Without changing any of these factors, you get the 'base' value for each. When you cast an Instant Spell (1 Turn), you take penalties to increase Factors. When you cast an Extended Spell (time depends on Gnosis), you have to get additional Successes.
All of these have to be determined before you roll; Instants because they remove dice, Extended because if you don't get the target Successes, you have to spend Willpower to re-factor the Spell to what you did get.
So think of rolling as getting paid on payday. Now what do you want to do with the money? Fuck it off at the club? Buy groceries? Pay bills? Just like you'd allocate money to different expenditures, you plan for Factors as penalties or extra successes.
So when we talk about Sight or Shield rituals, the Advanced Duration factor to reach a month is +4 Successes per the table on p.120. Now, remember every spell needs a Potency of 1, so that 4+1=5 Successes minimum needed to cast a Prolonged Spell for a month. Note that you can only used Advanced Duration IF you have 1 above the required Arcana. This means if you have Arcana 1, you can't used Advanced Factors on Sight -- you'd need Arcana 2. Likewise, you need Arcana 3 on a Shield.
- Determine your pool by Improvised or Rote casting
- Add +1 Arcana requirement if using Advanced Factors instead of standard/base Factors
- Subtract successes for an Instant Spell or Add Successes for an Extended Spell if increasing any Spell Factor