Petra,
Sounds like you are having some nasty bruises from your falls right now, and feeling frustrated and inadequate on top of it.

Everyone is different and will have different advice for you.
I would look at what is making me happy in my biking at this point in time and what is making me unhappy. I don't see stuff as a challenge that I necessarily need to "conquer". I don't see it as a failure/success thing.
I see things as just Things, they either aid my overall goals or hinder them.

So then the important question becomes- what is your Goal? Is your goal improving your technical riding skills, speed, power, etc? Overcoming obstacles or fears? Is your goal simply getting comfortable with riding your bike? Is your goal to just have a good time riding bike without fear and stress? Don't make decisions based on what others tell you you "should" be doing. Only you can decide what YOU are going to be happy with. And the beauty is that you can change your mind any time you feel like trying out something different!
There is no one choice. You can use the clipless system, or cages/clips, PowerGrip straps (that's what I use), or nothing at all.
But hey, at least let your wounds heal before you bash them on the pavement again- or wear some padding, girl!