Hello,
You have a mobile application, so that rules out AdSense, which is for web and mobile web sites.
I wish I knew more about the Ad Exchange use case but I don't know so I'm going to compare the other two for you.
AdMob and DFP both share the same SDK, but you'll set up your inventory on either the AdMob or DFP site depending on your situation. AdMob is the catch-all solution perfect for developers who just want to show some ads and start monetizing their app. DFP is generally used by bigger publishers who have direct deals with advertisers, and have more custom requirements on exactly how they allocate their traffic.
AdMob is probably what you're looking for. It is on iOS and Android, and also has a beta Windows Phone 8 SDK. I'm pretty sure it works in Egypt, though Egypt may not be migrated to our new console at
apps.admob.com. If Egypt isn't an option there, you can sign up at the old
www.admob.com site and you'll be able to migrate once the new console supports Egypt.
Cheers,
Eric