Budgeting for a Social Network

I have to submit a plan and budget for a social network and need help. I was asked to create a network with almost no budget (fun, right)? I've accomplished that and now need to present a plan and budget to my employer that will continue our rapid growth and move to phase two which is to monetize the site.

Pretty much everything I've done thus far has been a test here and a test there and I've figured out a couple of very successful enrollment initiatives that I will replicate all day long as long as the results continue. I'm looking for other ideas - viral or other (that justify an allocation) to include in a budget/plan proposal. Any ideas/suggestions/best practices to share?