That depends on how much money you want to spend! This is the maximum amount of money that Google will spend each day delivering your clicks. You should always monitor your daily spend to ensure that your campaign is generating revenue than it is costing (unless your objectives are not primarily financially driven).
If your campaign is delivering a positive financial result, then you should really consider increasing your spend to maximise your return.
If your campaign isn’t returning a positive financial result, then try to restrict your target geographical areas and keywords to improve the ROI.
Did you know that we run a ‘How To’ series for Google Adwords users?