I would like to create a site that that allows people to select a category and/or a sub-category and invite people to join and partake in something for a limited time period determined by the OP, but also allowing other users to suggest alternative options as a votable option.

I have no idea where to start with any of this.

Is it just forum software that I should be looking at, and could anyone recommend one if it is. Also how much should I be looking at to begin with?

EDIT - Thanks everyone, all good options to look at. I am going to try a Lemmy Sub, as that seems to be the most favoured answer by users. Hopefully I will get to grips with it. 🙂