Pretty easy project, with minimal tools. You' ll need a skill saw, jigsaw and drill. Materials would be any wood, glue, crews, stain and some felt.

Basically you' ll need 2-1x5 of pine, spruce or whatever you like and fits the budget. I would think 2 x 8 foot boards would suffice. You' ll need 2 pieces for the rack of about 3-4 foot long and 2 piece for attaching them together and to the wall (3 feet long would be ok, I think). Cut boards to length with the skill saw, then cut your 3 or 4 grooves(U shaped) at an angle in the side pieces with a jigsaw. Glue and screw them to your back boards( I would run a smaller bit to pilot the hole and prevent break out or cracking). Hand sand, Stain and add some felt (use a hot glue gun to secure the felt to the wood) for the grooves to protect the guns. Then attach to the wall in a stud. I would countersink the screw holes(for attaching to the wall) and add some wood plugs if in plain view to hide the screws.

Just get a picture of a gun rack and duplicate it. It would easily fit into your budget. Not sure what the price of wood is, but spruce, pine & fir finished(Planed) wood is usually the cheapest. You can put a nice oil stain on and some varnish...bet you it would look great.