Subtitle: There is no minimum budget required, but experience tells you need a minimum daily spend to let the system work.
Once your balance is re-filled, you may set up the budget you want. Budget (daily or Global) should always be above $25. In case your minimum budget is <$25 you may see your spend exceeding it, especially if you bid at a high CPM price. This is because of the time of synchronisation of servers. Please note that with such a low minimum daily budget, we cannot be liable if it is exceeded for technical reasons.