I just watched princess and the frog again after a long while and now im inspired to make a class or subclass homebrew for a warlock to make a voodoo witchdoctor like the Voodoo Man in Princess in the Frog but I have absoluetly zero idea on where to begin with creating a custom class/Sub class. I could really use some inspiration or direction to where to start with this.

Warlock subclasses typically match the following format:

Expanded Spell List: 2 spells at each level from 1 to 5 (they need not be Warlock spells)
1st, 6th, 10th, and 14th level features.

maybe you can get some inspiration from the Mystic Class. 

My opinion about this a voodoo doctor is either going warlock or wizard

Sure, but you might get ideas for Subclass Features.