Is there a way to get a true black in gum paste? Can I mix some black fondant with gum paste to start it off and then add more black if needed?

Any guidance would be greatly appreciated!!

I am not sure if this answers your question...
I add SuperBlack colour to my white gumpaste and have had great success.

If you add black fondant to gumpaste, you'll get grey and you'll also get a softer mix (which is a good thing unless you want it to harden quickly).

you could try buying black fondant and adding Tylose to it. Would harden up nicely and no hassle of trying to create a true black. good luck