Step 1: Draw Out Design
First you have to draw out what you want it to look like when it's all put together. Look on line for pictures that represents your costume.
Step 2: Make 3D Maneuver Gear
What I did is I got two 20" by 3" by 2" boxes that I cut out. Next put any color duct tape on them it doesn't matter because it's going to get spray painted later. Then get two bottles and two cardboard rolls doesn't matter what. I used sunny d bottles and rolls from paper towel rolls. Use duct-tape over them to tape them to the maneuver gear boxes so it looks like they can slide in and out. Then attach twos other strips of duct tape to each side of the gear so a belt can slide in and out have a 1" space between them. Now spray paint it silver. Gear done.
Step 3: Make Harness
Go out to a thrift store and get thin cheap belts. About 6-8 will do. A good way to attach belts together is with a Hot glue gun.They have to be at least 20" long. First make the top. Either find a belt that fits around the top part of your chest or cut it so it fits. Then attach two belts to each side of that belt where your shoulders are. It should look like picture 2. Then make the bottom part remember to always mark where each belt piece should go. And your going to have to cut belts. Start with a belt to go around the waist where a normal belt would go. Then cut two belts that extend down to your thighs this is where the maneuver gear goes. Then measure two belts around your thighs. Cut it and make sure you cut the part with the buckle on it poke a hole in it so you can strap it. Glue the thigh belts to the normal belt going down the outside of your leg. This next part is complicated to explain so just look at the last picture. Then your done if the glue comes apart use glue.
Step 4: Make Clothes Part
Go out and buy or make tall brown boots. Go online is the easiest way to buy a survey corps cloak. Next get a brown colored shirt or buy a real online attack on Titan one. You need white pants and that's it.