When you're talking about costuming, I learned that it really is not as complicated as it looks. What we see is just the finished product. Most of the clothing started as pieces from Goodwill or the Salvation Army as you can find cheap clothing there that works for the base pieces. You can also get fabrics and leather from your local fabric store. Ask the people there for help because a lot of times, they will be able to give you good advice on what kind of materials you are going to want to work with. You need to keep in mind that you are planning on wearing these clothes for long periods of time, so make sure that you design your costume so that it is not only comfortable, but so that you are able to move around in it easily. You also need to remember that you might need to wash these clothes, so make sure it is washable fabric. The number one thing they said to remember is to bathe! You also might want to take into consideration how much time it takes for restroom breaks and if you will need help getting in and out of your clothing, so you might need a bathroom buddy. A good rule of thumb is to just wear your costume and full armor around the house for a while and make sure that it is comfortable. They did say that you are probably going to want to buy shoes and not make them. You can get shoes that fit the era quite well and given how long you are going to be on your feet, you don't want to be miserable at the end of the day.
The leather armor and stuff that is on top is really not as complex as you might think. Basically, anything can be used for steampunk materials. I know I recognized the copper plate and fan from a video card on one of the arm cuffs. They said that they'll just take broken things, watches, egg timers, you name it, and take them apart for the pieces. Make sure though that if you are just taking things apart in the house to make sure that no one else there actually still needs that. There was one gadget that had part of the kitchen sink and one costume that had her mom's tablecloth (which did not make her mom happy!). Kid's toys are very good for gleaning pieces and parts, but they also cautioned to look out for "Steampunk Landmines." A steampunk landmine is usually a gadget with large springs that are tightly coiled. When you go to take these things apart, you need to be very careful because once the tension is off of those springs, they have a tendency to pop off and can seriously injure you as the ends are quite sharp. You need to know your tools and the materials that you're working with. Just be careful when you go to take things apart and use caution and common sense.