what website/software would be best for me?

I'm really new to website building. I have an idea that I want to create, and I'm trying to figure out what free software packages such as blogware and wordpress would actually get me to where I want to go.

I want to create a site or even a blog where there will be several categories with tons of information within each section. I want anyone on my site that creates an account, to be able to add whatever insight they have to whichever category they choose.

I've been told by some people that wordpress would allow me to do this, but that I wouldn't be able to put my own ads on the blog? I'm not exactly sure what I should do here.

Thanks for taking the time to read all of this.