This depends on a whole range of factors, so I can’t give you a straight answer. That said, I can give you a way to get the answer you’re looking for.
The number of ad plays you get for your budget is dependent upon the cost-per-play for each board in your campaign. It’s actually quite easy to calculate - it’s just your budget divided by the cost-per-play of the board you’ve chosen. This would be fine if the cost-per-play stayed constant, and if you only had 1 board in your campaign. The reality is, the cost-per-play of each board varies by the time of day. You also rarely ever have just 1 board in your campaign either.
So how can you solve this problem?
Go ahead and create a campaign. Once you’ve picked your boards, you’ll get to choose your schedule and set your budget. As you vary your budget, you’ll be able to see a projection (at the bottom of your screen) that shows you how many ad plays you can get for your budget.
This is the most accurate projection you can get, because it is based on the specific boards you want to advertise on, and the exact times of day that you’re after.
Head over to the Cost Estimator. Pick the types of boards you’re after along with the number of each board type. Vary the number of hours in your campaign and board counts until the suggested budget is close to what you’re expecting to spend. Then, use the projections to see approximately how many plays you might get for your budget and board types.
This is a very rough projection - super quick and dirty, so use this at your own peril. I’d certainly recommend Option 1 if you have the time to do it.