Money is a big problem, but the national LP gathers it from the entire country to spend in the states needing expensive signature drives.  There are wealthy libertarians who donate several thousands at a time, but no billionaire funding.  The sources of the money raised for this purpose are public record, I believe, and can be obtained from FEC filings.  I don't see why you assume that a national political organization can't raise the money needed to do ballot drives without help from some billionaire.  We had 47 states in 2012 with no money but our own. We'd have had fifty if not for GOP scuttling of our efforts in three states.  
I don't want to speak for the Greens, but I have heard they don't accept large donations even from wealthy folks who completely support their agenda. This would make funding anything bigger than a state legislative race difficult. Perhaps they are now more open on this point.