Hey!
You can do with 100$ as much as you could do with zero but it will just save you some time.
Depends what you want to do, try to spend it only when you really have to and try to cut costs as much as possible.
Possibility is you could hire some people, get some software or a service, to start selling something.
Find something you want to do and then do it, 100$ can be helpful if you are smart with spending it.
I wish you good luck!