Follow blogs on my multisite network

Hi, i use multisite on my betly.info wordpress site.. to allow users to create their blogs on my site subdomains.
How to add follow button to every blog on my network to do next, when every registred user click follow he becomes follower of course ?? and on main site betly.info when he is loged in to be shown widget with links of blogs that he follow. or somthing like that to do that idea (blogs that i most visit, recently visited blog)

i already use latest network post and recently updated blogs.. but i need something personal like that to users can easier find blogs that they already read.