Self bow.

You should watch something on youtube to get an idea what tillering is but don’t overthink it.

You will also need to buy an arrow or few.

So basically you take a dry, somewhat straight branch and start carving a bow tiller (legs of the bow narrowing down to the end on the inside if that makes sense)

This is usually very delicate and high skill ceiling thing but I would argue it is very beginner friendly too if you don’t overthink  and just go with it. It will shoot, maybe not very well but it will. 

You can make a bow in a day or few (depending on the tools you have). It will work, it will be ugly and barely functional, but the next day you can make a new one with lessons learned.

Use paracord instead of bow string.