Hi Andrew. There are tons of resources available. Its a stormtrooper that your interested in? First and foremost, i strongly recommend heading to www.whitearmor.net.
There you will find everything you didn't know you need to know from vetted suppliers to tips & tricks of building. Remember, there is no such thing as a stupid question except the question that goes unasked.
Once you are in there you can see all the current costumes approved for wear and the specifications for each one.
The information on Whitearmor can be daunting and may seem overwhelming, but once you get used to the forums it is pretty straightforward. Also, there is a semi-official saying in the 501st "Troopers helping Troopers." If you have any questions feel free to reach out to us and we are more than happy to help. We have all been where you are right now.