I'll email you something that might help you get started. I'm a second year treasurer and a HUGE fan of a well-defined budget. I have found that it eliminates much of the emotion of the PTO - that is, people can't finagle their personal agendas for spending when the plan is put in place at the beginning and any change must be approved by a vote of the membership.
A good place to start might be your records from last year. Did anyone do an annual report for last year? If not, go through the records. Add up your expenses in different categories and then you'll know approximately what you'll need spend in each of those areas this year.
I am the treasurer for our PTO and budget is not even in our vocabulary. For that matter, Organized doesn't seem to be either. I would like to set up a set of budget guidelines for us to vote on and use but have no idea where to start and what all to include. Can anyone share budget plans so I can get a starting point at least? Our fundraiser that we had this week (we held the concession stand for the UIL meet) didn't make us nearly what it should have made. We made $1600 off the sales, but after all our expenses of $1200+ we profitted less than $400. I have sat down and figured this and our profit was reduced because most of what we sold (candy, etc) wasn't priced properly so we only made a few cents off each item. Anyway, I think we need a budget and more planning to keep this from happening in the future. Thank you!