Why do magic users have staffs? Well for one, they can use them to knock the head of the monster in front of them but why would a magic user ever plan on being on the front line? They don't.

Here's then where we introduce foci and staffs. A focus is a gem, usually flawless and therefore expensive that can be used to store magic energy. The size and value would necessarily have an effect on its potential.

For each turn, you may charge a focus with any level magic it is capable of up to the capacity of the gem and it can store that energy for an hour or so without dissipating. The advantage is, before a fight, you may charge it with spell points and therefore ready a spell that might otherwise require some time to cast and cast it instantly instead. Additionally, it can be used to build up to a spell point, say if cantrip level energy, heretofore it is 1/2 SP is charged in one turn, then in the second turn, you may cast a spell that would otherwise take 1SP but for free, basically taking two turns to make up for not having any spell points left up to the spell level you can normally cast.

So Ashley could conceivably cast "summon necrotic rats" every other turn rather than the wasps every turn. It's pretty well balanced in that case, given she had a focus.

A focus can be in a ring, an amulet, a tiara, a wristband, a staff, a sword, or simply held in the hand.

What gems qualify? 100gp or more, flawless. Size matters.

Using a gem with flaws has a chance of destroying the gem and backfiring. In Ashley's case she risks taking necrotic damage, but since she's immune to it, it would simply destroy the gem.

In the case of a staff, the damage radius would have to be enough to reach the caster, a long staff would be enough to negate damage from most spells to the caster.

In addition, it can be used as a quarterstaff would though in Ashley's case she wouldn't because she's a pacifist.