How do you increase spell use in dark souls 2?
Solution 1:
Leveling up the Attunement stat will give you extra spell uses. There is also a ring that grants additional spell uses, it's called Northen Ritual Band
I hope this helps
Solution 2:
You can also slot spells in multiple attunement slots (given you have the slots). For example, lets say you have 2 attunement slots, and you have two "soul arrow" you can slot them both (1 in one slot, the other in the other slot) and get two times the uses.