The stuffs below are found randomly over at the Internet.
I recommend you do the same, look around in Google, Youtube and others.
(Read me) Cosplay Guide for Beginner: Kotaku
DIY Cosplay Crafting is all at your own risk, at the cost of your own money, time and efforts.
Search in youtube for more step-by-step tutorials on how to make cosplay stuffs.
Eva Foam seems like an interesting material because you can create imaginary items. You can purchase them from shops or local suppliers. Try to test out some basic tutorials, which can be found on youtube, like on how to make a sword or shield first. Then bring them over at Cosplay events and show your crafted items to your friends.
Dressmaking can be a bit more challenging, because doing this and trying to get it right on the first try would prove to be a little more difficult. That is why most Cosplayers commission their dress outfits because it needs talented handiwork skills. This is the same for leather tailoring as well. Both materials maybe different, but if you do not mind making it yourself, then good luck because its fun exploring new things.
Crafting armor materials may take more time because it all goes down to the details, shape and design. You can use the same material from Eva foam, or from other composite materials or recycle materials. Also, do not give up too soon because most first time crafter do not get their armor props on their first try, some even after years and graduate improves. It takes loves and passion when it comes to armor crafting.