Questions regarding VPS,VPN, and Proxys and there roles doing different tasks in IM/SEO

I have done quite a bit of studying on the subject and do know the differences and uses of these in IM/SEO related things but still had a few questions I hoped I could get answered....one thing I am wondering is,if you are running multiple social media accounts from a VPS, would you use one private proxy for each set of accounts and just keep those proxys as long as you are using the account? So for one twitter account,one facebook account and one pinterest account I would manage the three with one Private proxy and for each additional set of twitter,fbook,pinterest I would use a different private proxy and use the same proxy as long as I manage the account? In regards to SEO I know that a private proxy will not last you long so I am wondering if this is the case when running multiple social accounts with them. Also would it benefit you to run a VPN to your VPS,then a VPN out of the VPS and private proxy afterwards when running SEO campaigns or managing multiple social media accounts? Would a better way to do this be Get different VPSs with multiple IP's to manage social accounts? Can you simply run SEO campaigns(SeNuke/Xrumer etc) from a VPN? I know this sounds a bit scattered but I am really trying to grasp the concepts and uses as I realize it is a fairly important thing to be knowledgeable about when it comes to IM/SEO/Social Media......thank you in advance for any replies.