Text on each screen/slide

Hello - I'm still relatively new to creating online courses and am hoping you can point me in the right direction on this:  I'm working on a course that is an intro level into global mobility/relocation.  It will be taken by people around the world - all in English.   I'm having trouble figuring out how much text I should have on each screen and how much to just leave to the narrator.   I'd prefer to stick primarily with bullets and have the narrator read the entire sentences in order to keep the slide looking not so busy (the whole "less is more" thing).  Are there any rules of thumb on how much text to keep on a slide?  (I'm using Presenter).

Thanks in advance!!