I liked the kit lens for lenses, with a hacked-together light box, sunshine, a tripod, f9.5 to 11:
I think a macro prime lens is probably overkill for something boot-sized and in an online photo. It's unusual to see online images larger than say 1800 pixels wide, so everything will be resized and that fixes a lot of sharpness issues. As already mentioned, zooms offer flexibility - you aren't constantly moving the tripod for different framing.
Are you shooting the boots by themselves or on a model? What's your lighting going to be like?