do I need the multicam ACU's? I have both the popland and digital Camo from when I was in the marines will either of these work? And do you have a standard weapon for the team?
You can use whatever you want while trying out for the team, but Multicam is the team uniform and all the patched players are expected to have it. But it generally takes 3 to 6 months to make the team. Come run with the team and see if it's a good fit for you before worrying about camo.
As for weapons, we standardize on magazines, everybody on the team with very few exceptions carries a gun that uses M4 mags. But each persons weapon is slightly different, whatever works best for them.