I'm looking for: The right bag

I'm done with buying bags that are too heavy just because they look good or from a specific brand. My back is after all the one suffering and consequently my mood is not at its best. Many of my bags are heavy even when empty and that's because the leather is too tick. From now on the first quality I'll be looking for in a bag is its weight.
I also appreciate flexibility in anything I buy and all these bags do it for me. I can carry them either on my shoulder, arm or hand. The price also makes sense to me.