I am not familiar to Poliigon and it’s content. But generally a gloss map is the equivalent of an inverted roughness.
So either open up the gloss map in an image software and simply invert it and export as roughness, or invert it in the material (not as clean and generally not preferred)
As for the reflective map, there should be no need for it in a PBR workflow. But it’s the equivalent of a specular map:
Hope it helps!