In order to get started in making props, a few things are necessary in my opinion.
Those are a hobby knife, foam, glue, and paint.
Hobby knife: Any will do as long as it is sharp and has replaceable blades.
In a pinch, a box cutter can work; sometimes using a box cutter is easier if you’re doing larger cuts.
However, you may run into some trouble while trying to cut smaller pieces out.
Foam: EVA floor mat foam is what you want for larger props and cosplay.
Use hobby/cosplay foam for smaller/thinner pieces. at the time of writing EVA foam can be found cheapest on Amazon,
about $20 for a four-pack, and cosplay foam can be found at Hobby Lobby and other craft stores.
Glue: I’d recommend getting DAP Contact Cement for gluing large items together.
DAP is flexible after it dries, which makes it great for foam.
Hot glue and super glue will also work for large pieces, but both have downsides.
Hot glue can melt the foam and won't stick very well when gluing large pieces,
and super glue will become rigid after drying, which is not great for a flexible material.
Paint: Foam is an absorbent material, similar to a sponge; therefore, it is a must (in most cases) to prime the foam before painting.
Personally, I use the spray-on Plasti Dip. I’ve seen other people use the liquid Flex Seal, and it works well for them.
After priming, you can then use most any spray paint. Spray paint will crack over time, so if you’re painting armor or
an item that will be moved and handled a lot, I'd recommend Plaid FX paint. (If you use this paint, you don’t have to prime
because it is specifically made for foam.)
Other optional tools (All of these tools are optional. While they do make some things easier, you can make awesome-looking pieces with just the essentials):
Respirator - if you’re working in an enclosed area with DAP Contact Cement or spray paint, this is a must.
Knife sharpener - Foam dulls knives very quickly; if you want to get clean cuts, I’d recommend sharpening your knife every 3-4 cuts.
Self-healing cutting mat - this is great to cover up mistakes or imperfections in the foam, Dremel, and a belt sander.
Update as of late 2024:
I have invested in two 3D printers: an Ender 3 V3 SE and an Elegoo Neptune 4 Plus. I’m planning on getting an Ender 3 V3 soon, as I've had a frustrating time trying to get the Elegoo to work properly.
Furthermore, at the time of writing, my Elegoo is out of commission, and I'm waiting on replacement parts. 3D printers are extremely useful in prop making.
They allow you to achieve details that would take hours of carving and sanding foam in just a few hours of print time, while you can work on something else.
It’s very handy. There are also thousands of 3D printable files available for free online, which can save time on 3D modeling or even eliminate the need for it if you find a file that works for you.
If you're getting into prop making, I’d still recommend starting with foam and basic materials. But once you have those skills down and feel confident in your work, I’d highly recommend getting a 3D printer.