Things you want to learn and enjoy playing is the best to do when you're starting out
As for where the notes are; in my mind I visualise a guitar fretboard, combined with a piano lay-out. It doesn't really matter how you do it, I reckon, but you'll need to find a way that's useful to you. A guitar (or bass guitar) is quite logical in one sense, because it's just all the notes from low to high on a string for example, but actually quite difficult in another, since the same note can be found in more places.