Is a third resource too complicated for a Pen and Paper Strategy Game?

Instead of having individual Energy totals for spellcasting units, I decided to have workers mine magic Crystals which are then spent as "spell ingredients". Problem is I've already got two resources: Gold and Oil. Adding Crystals for a third resource might be getting too complicated to solve by hand. I don't know that average people are willing to do this much arithmetic to play a game.

Presently, "Force Field" costs 25 Crystals and gives the target unit 100 bonus HP and +2 bonus armor, while "Rain of Fire" Costs 75 Crystals and does 50 damage to all enemy units on a target space within 3 spaces of the caster. These are examples of how I'm using the Crystals.

I estimate one game takes between 30 minutes and one hour to play to its end, unless the losing player concedes early anyway.

Is a third resource too complicated for a Pen and Paper Strategy Game?
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