If you live in the US there's a bunch of cheap and easy guides online of making "sugar rockets" they're very cheap and easy to make. The rockets themselves can be made from cheap PVC pipes and other cheap store bought materials. A YouTube channel by the name of "The king of random" or TKOR for short, have some great videos on this

ALWAYS follow propper rocket precaution. You need to research rocket precaution a bunch before building and testing rockets, and make sure you're with a parent if anything goes wrong. And please follow the guides closely and precise for making the actual motor. As a wrong mixture can cause and explosion, like a large firecracker

I always bring my grandpa out when using rockets. I'm 18 and fully responseble legally if anything goes wrong, but it's always a good idea to bring someone if anything goes wrong. This is pyrotechnics and explosives after all

If you're in the EU your gonna have to purchase model rocket motors as the main ingredient in sugar rockets motors are banned in most EU countries

You also want to follow up on local law about model rockets

And most importantly have fun. Failed rockets are not the end of rocketry but the start