Join Date:Joined: Jan 2014
It's perfectly fine to use multiple ads providers. Using admob meditation would be the easiest way to go. Also - depending on the development environment you're using - there might be already plugins to connect with other ad networks, so it's worth checking.
BTW - I don't have any stats to back me up yet, but most of my friends claimed that admod outperformed other ad networks in terms of income generated. Please share your experience.