Easy trophy to get. All you have to do is go to Ammu-Nation and find a weapon the cheapest weapon and purchase all the add ons for it along with the different colors. If your PSN is connected to the Rockstar Social Club, you can get this trophy without spending any money. When you go up to the counter, look to the left and there should be some weapons. All of them are free to social club members. Just add all the modifications to the weapon(s), it should be free. Then Bam the trophy is yours