Keep in mind that learning Multisite and BuddyPress is a process. While it is easy to set up, managing a community and a network of sites is harder than you think. BuddyPress has more features than a new site can really use so you have to plan a deployment strategy to prevent your users from being overwhelmed. BuddyPress and multisite is not a situation of "if you build it they will come". It require planning, maintenance, care and plenty of work. Just know that to do it is not like running a blog, it is an entirely different level of management and administration, something you have to be committed to for the long haul.
There is no simple answer to your question because the answer itself is far too complex. You could certainly set it up, but if you are not prepared for the things I mention above, then you can almost expect the sound of crickets and spammers on your site.