Hello,
You can get all account budgets with the
BudgetOrderService. With the result (you get all budgets, including budgets of past and future), find out the active budget. That result will tell you the start and end dates of the budget. To find the spent budget, simply run an account performance report for the period of the start date until today - and ask for the cost field. With the active budget, and spent money you can calculate the numbers you need.
But:
1. BudgetOrderService needs a whitelisting - you need to whitelist the MCC containing the accounts on which you want to use the BudgetOrderService. Contact your Google representative for this.
2. This does not work on accounts with video campaigns. Money spent on these campaigns is not reported by any report.
Hope this helps.