If you could make a 2X return on your advertising, what would your budget be?
This means, for every dollar you spend on advertising you could gt $2 back, after expenses. My guess is you would spend every dollar you have.
This is the way advertising should be. As long as you know you can make more money from advertising than it costs to advertise, than you should be willing to do so all day long.
Instead of looking at advertising as being a cost, look at it, done properly, as a profit center and instead of trying to figure out if the advertising fits into your budget, figure out how to spend as much as possible on the most profitable advertising possible.
Have a great day!