There are at least three different easy DIY approaches to making your own stakes, not even mentioning all the lightweight alternatives, like using chopsticks or long aluminum nails:
Cutting from greenwood. Easy, cheap, biodegradable, and what you need is a small knife and a fire for hardening tips on it. Problem is they are heavy, big and if they're not - they break easily.
Bending aluminum rod. 4-5 mm diameter will work. Take a rod, cut it to 20-25 cm pieces and bend a hook on each one. They bend easily (you'll need more than a multitool to make them though), but it's easy to plant them deep into the ground
Cutting L-shaped aluminum profile. Probably second strongest after using greenwood. Take inspiration from any commercial pattern.
Good file sufficient to cut thin aluminum stock, you won't need any power tools.
You can anodize aluminum - search and you'll find, it's really cheap and easy.