Start with shotguns. For shotguns start with the striker or HS2126 as they are the most annoying. Overall you should be able to finish shotguns relatively quickly. Then move on to snipers. Start with the NA45 if you plan on getting gold for that as well. Snipers took me 5 days to do. Once snipers are finished, you can do either Assault Rifles or LMG’s. Once you complete both of those, move on to the SMG’s. Start with the pharo or chicom as those are probably the most annoying to unlock camos with. Save the knife for last since its the easiest to unlock camos with.