Ahmad,
It is normal to see test ads once you have integrated. You should be able to see actual creatives from AdMob once the ad network is setup within your MoPub dashboard. It would take some refreshes to get the ads cached but then it would be serving to your simulator.
Another way to test the type of creatives that are coming in is to select ‘Test Ad’ in the Inventory tab over at mopub.com. In the Chrome browser, content may be blocked from being loaded. A shield icon in the address bar will appear. Click on the shield and then click on ‘Load unsafe script.’ Then click the ‘Run Again’ button.
You should be using your AdMob's 'Ad Unit ID' and not the 'Legacy Publisher ID.' I know it may be confusing as within MoPub's dashboard it mentions to have the 'Publisher ID' but really it should be the 'Ad Unit ID' from AdMob that should be entered.
Please consult this guide for more info: http://help.mopub.com/customer/portal/articles/1376821-how-to-set-up-updated-admob-revenue-reporting
Do you have marketplace feature enabled and seeing request/impression counts coming in?