I think you need to think about what you want your site to be. Do you want the site to be a discussion site? If so, then you will want forum software such as XenForo. If not and you only want to publish information, then something like Wordpress would be better. If you want both, then you may require both of these.
Running a site requires a domain name (which you can buy from various sites), web hosting (again, various places offer this) and of course the software you require to run the site. You'll need to know the basics of how to manage and run a site (how to upload files using an FTP client or possibly cPanel or similar that's supplied by your web host). You'll also need to know how to set up the software to work as you want it to for your site (configuring stuff in the admin panel). It's likely that you will also need to know some CSS/HTML if you are going to do some customisation of your site's appearance. You can purchase themes for your site as an alternative but you'll likely still need some basic CSS/HTML knowledge.
If you think you can manage all of that and you're still interested in XenForo, you can set up a demo to try it out before you buy - the link for that is on the XenForo home page.
