I didn't mean checking the FAQ topic for an answer, I meant checking with Bull in his FAQ topic. I made a post to doublecheck.
I understand a character who goes low on Magic and Spellcasting would not be able to score 5 hits but only 3 (assuming the same buffs the character I mentioned would need for Force 5). However, that still lets you boost Rating 3 Attributes to 7 while avoiding Focus Addiction and Sustaining penalties, and you can still overcast Force 6 spells and Quicken those when it comes to Detection and Manipulation Spells. If your Reaction and Intuition are low, you can boost them to 7 and have 14 dodge dice and 14 Initiative, a Force 3 Increased Reflexes spell still adds 2+1d6 Initiative, Combat Sense would still add dodge 2 dice at your base 8 dice, Armor would still add 2 armor, Levitation would let you levitate 400kg so yourself +300 kg in carried stuff, and so on. There's still plenty of tricks to be pulled and buffs to be obtained even at a low Force. Plus it's the only way for you to heavily buff yourself with magic spells.
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As for minmaxing without buying hits:
The minmaxer at 20 dice who uses Reagents to set a limit of 12 could take the spell and roll several times, until he manages to score 8+ hits at 1/3 odds. He then rerolls 12 hits and aims for the 60% odds at 4+ hits, has to resist 12P drain in the case of Increase Reflexes and Quickens them for +12+4d6 Initiative. Meanwhile, the 3+5 character only has a 25% at +6+3d6 Initiative with Edge, which means only 60% odds at being able to do that in a Session when they didn't use any Edge on other things. With normal casting, their best bet is 4 hits since any more would take far too many casts.
So the minmaxer scores an easy 12 hits, with odds at more if they use reagents and are willing to risk getting knocked out by the drain. (If they first quicken an increase to their drain dice and increase their body as well, even 15P drain has hardly any chance at knocking them out.) Meanwhile, the weak caster is still limited to just a few hits more. So the minmaxer can score an AWFUL lot of bonus and the weak caster only benefits a bit more.
At that point sorry, but I think that when both the relative and absolute impact are much better for minmaxers and minmaxers would become an absolute disaster, buying hits for Quickening is the only fair way to go. Otherwise methods have to be made to fight off people walking around with +15 Armor, +15 Dodge Dice or +15+4d6 Initiative, which also hurt the weaker spellcasters that want to use Quickening.
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As for not taking Foci: Why not? I can understand not taking Sustaining Foci, but why not take Force 3 Spellcasting Foci? You wouldn't need more than 1 active at the same time anyway, so you wouldn't have any trouble with Focus Addiction.