Display RG Locations based on State, City, Zip selections

My customer (Retailer user- enterprise) has a List of Locations (all locations). When the User creates a new Gig Post, I need him/her to select the specific Locations to which the Post applies.

For retailers with thousands of locations, it’s probably more efficient to let them first choose the specific States, then deselect Cities within the State and then deselect Zipcodes within the selected Cities in order to arrive at the locations to which the Gig applies.

From the attached image, my desired goal is to hide Cities until at least 1 State is selected, and hide Zipcodes until at least 1 City has been selected.

I have custom states but not sure if they should be texts, or Locations. So once at least 1 State, City, and Zip is selected, I don’t know how to match add the Location(s) to the Gig posting.

Any help would be greatly appreciated, thanks!