Creating a Member rich Network

I am trying to create a network for a niche education subject.

What I would like is to have members sign up and participate, via Buddypress, in discussions, etc.

I am having trouble with spam, so I closed membership and also have deactivated the ability for new members to create a blog upon signing up.

I would like, however, to allow two basic levels of membership for free. The first would be basic where members would sign up and be able to participate in the social network (Buddypress). The second would allow participation in the social network area but also allow for them to create their own blog (for teachers who want to update their classes, etc.).

After this, I would like to incorporate more bells and whistles for those that want to create websites – premium plugins and themes – which I could make use of the Pro Sites plugin.

I am not exactly sure how to navigate this and get my project refined to this point though. Any guidance or suggestions on how to set up a project like this would be great.

Thanks in advance!