I'm one of the guys to talk about helmets, what is important is that you get one that is the right size for your frame, though I am making a smaller size, if you get a 1:1 and it's too big, you've spent a whole load of money on something that makes you look like a bobblehead. The other option is a 2 piece Jango helmet, which is smaller than the 1:1 and not as good quality as a fiberglass bucket, but it might be good enough for you.
If the outfit is just for you then fine, but I would take a look at the mandalorian mercs CRLs just to give you an idea of what you need to sort out an outfit, especially if you are doing it for film.