First comes the original three OVAs (Eternal Story, Destruction and Stardust War, in that order) and then the Earth Force chapters take place afterwards. Way afterwards. It'll make sense after you see the original three OVAs. Personally I liked the original three, never seen much of the Earth chapters. You have to be able to appreciate late 80's OVAs, since they reek of that era.
Check them out, just understand when they were made and they should be enjoyable.
Oh yeah, I believe Rhea Gall Force is the Earth Force chapters.
Gall Force OVA 1: Eternal Story
" 2: Destruction
" 3: Stardust War