Ive been thinking... and here is about the most efficient way to acquire spells.
Now lets say you use the sum-to-ten system (the only way to get any reasonable amount of money) and set money and magic at a, race and skills at e, and attributes at c. (you can come close with point buy, but you end up with lower attributes). The absolute most efficient means of acquiring dice for spells would be to buy specific spell foci at 1 force 1 and then buy spell category foci, but doing so pretty much requires that you limit yourself to a single category of spells. As a starting character, you can get a force 6 spell category focus for 450,000

This does not grant the ability to cast any spells. Each spell costs an extra 45,000 nuyen... so lets say you get 7 of them. That costs an extra 315,000

. At this point the mage has used up all of his starting spell points. He no longer has enough money to get better than a force 2 spirit focus, so he decides to get a couple of sustaining foci, using up the rest of his money buying the foci and the spell points to bond them.
Thats not too terribly bad. The alchemist knows 7 spells, with the ability to throw between 11 and 13 dice into each one if he needs to. It is certainly not great, though. Each additional spell will cost the alchemist 90,000

at the very least... and if the alchemist ever wants to learn a spell in another category, it will be *much* more expensive. Furthermore, the alchemist can not summon any spirits, and each die he wishes to use to summon a *single* type of spirit will now cost him 120,000 nuyen and 2 good karma.
This is all assuming that the force of the spell is not limited by the spell category focus. I would say that limiting the maximum force of a spell to the alchemist's magic attribute would be a reasonable counterbalance to the incredible limitations they have on learning new spells (do NOT allow the alchemist to cast spells at any force whatsoever). If the maximum force of the spell is limited by the force of the specific spell focus, the max number of reasoably good spells a starting character could have would be around 4, and thats also not including the ability to summon spirits.
Finally, if the alchemist is ever deprived of his foci (captured, for example) he will be all but worthless until he acquires the hundreds of thousands of nuyen to replace his losses.
Its certainly an interesting idea, but its not one that I would ever use. The flexibility implied by being able to cast any spell or summon any spirit is mostly illusory, as very few characters will come close to gaining any real breadth of ability until after years of play..