If I were you I would stay away from "tacticool" guns and expensive gear, unless you want to invest in them purely for advertisement purposes. Everyone wants to see a $2700+ SCAR Heavy up on the wall buy will anyone buy one? Probably not. I would focus on guns you will sell a lot of low/mid/high AR platforms, common hand guns and accessories, think of things people will want while they are shooting, not things they could wait and order for cheeper online.
Also, as much as I personally hate it if you require customers to use store bought ammo you might drive away a few die hard re-loaders but for the the casual shooter they will just buy it from you, and that improves your bottom line on ammo.