In my game Hyperblox, for example, I have two "in-house" ads.
The first one is displayed once, when you start the app.
The second one is displayed whenever I want.
Bear in mind that these ads are nothing more than clickable images. In my case I'm using PNG's because I like transparencies. These ads are fully dynamic, I can change them whenever I want, since they're stored online.
The updates are done from my PC via FTP (Filezilla). There is also a text file on my server, which controls their behavior. Both ads have an expiration date, an optional hyperlink, a "forced update" option and a "chance of being displayed" in percentage.
Why do I have this percentage going on? Well that's the clever part, since I'm also using AdBuddiz.
For example, a 100% chance rate will always display the "in-house" ad instead of the monetization ad. This way I'm able to balance between advertising my own stuff or making money with AdBuddiz. To change this value, all I have to do is to edit the online text file. A 0% value will deactivate the "in-house" ad.
Assuming that you know how HTTPUtils2 works, here's my system's flowchart:
Sorry I'm not posting the complete source code. This explanation should however, point you in the right direction.