As a digital marketer, one would like to have a good FB cover or blog graphic or anything related to digital world that would enable you to present your product / service well. Your search for these things can be realized easily by visiting Canva in beta.
You can learn the various design techniques by clicking here. It is online and free to use and lets you collaborate with anyone, anywhere.
The following video suggests a snapshot of what can be done using Canva.
Do let me know what you feel about Canva.