The reason I made this app is because I kept looking at my clock while studying, and I got tired of seeing so many white letters on the black. So I wanted to decorate my clock in my own style, so I developed it.
I’m not good at English, so I used a translator. I’m sorry.
What kind of ads are there? Because that might ruin the experience.
I can’t imagine very many people wanting to watch a clock with ads.
It might be better to take out the ads entirely and use In App Purchases. Give users basic functionality and the ability to change a few colours, fonts etc. Sell the rest as a cheap IAP. You will hopefully make some money that way.
Ads should be avoided wherever possible especially when their placement doesn’t make sense. I think ads are inappropriate for a clock app like yours.
Ads are best used in games (between levels) or other apps where you have to take multiple actions so you can show one every few minutes. Banner ads can also be used in those types of apps because people expect them and the ads don’t ruin the UI.
But in a clock app the ads will distract from the UI (the time itself) and people will use another app that does not have ads in it. This means you will not make much money. Also it may appear cynical - there is not much to a clock app so having it running and showing ads may make it seem appear that your prime motivation is making money.
With IAP there is a chance you might make something, as long as the content has a premium look and feel to it. With no ads and a clean UI more people are likely to use your app and some of them might pay for the extra content.