The samurai fighter costume can turn any teenage boy or adult man into a tough looking samurai. This is quite an extensive costume which has many parts and layers to it; including clothing, armor, helmet, sword, and waistband.
You will want all your regular clothing for the costume to be made of polyester material, preferably black polyester. You can start with a long sleeve shirt and long pants with an elastic waistband. If you can find some polyester black gloves, then that will be good too.
Next, you will focus on the armor. There are many separate pieces of armor that you can use for different areas of your body. The full costume could have armor for your shins, knees, shoulders, torso, forearms, and upper legs.
If you don't purchase this armor at a novelty store, you can purchase Sintra poster board and create your own armor out of that if you are creative enough. You can color the armor red with a gold colored outline, although there are really no set colors for this. Use your own creativity for the colors.
As for the helmet, it can be metal or plastic which closely surrounds your entire head except for your face. Think of the Darth Vader helmet from Star Wars but without the facial piece. The part of the helmet that is over the forehead area is called a crest. This is supposed to symbolize the rank of a Samurai warrior.
For decoration, just use a metal U-shaped object and attach it in reverse on the forehead area of the helmet. Finally, go out and purchase a samurai prop sword. They are made of plastic or stainless steel in most cases.