There is not much to be gained by only shooting manual, and you will learn about your camera just as quickly by using aperture priority and shutter priority. It's almost the same, but with one bonus: the camera will show you how changing one setting will affect the others. Modern cameras are "perfect teachers" in that sense. No need to rush into manual settings, unless you actually have an old camera. In that case you have to prioritize either aperture or shutter speed, but manually :)

Start from the f16 rule: On a sunny day just use the same speed of your film iso (asa) and f16. Let’s say 400 iso (asa), speed 400 and f16. If it’s cloudy go down one stop. U need to know stops of exposure and depends on which camera you are using but you help yourself using the light meter you have in most of them.