Great question, bbwebmaster
I used to asked this same question when I was in more offline business. Whenever I met someone successful I would get into the conversation, as politely as possible, about how they made a success of themselves. Invariably they felt flattered and, therefore, spilled the beans. I picked up some great tips!
When I started I had just sold a little company and was running other little businesses. However, I chose to invest virtually nothing, other than time (opportunity cost) in fear of getting ripped off or making enough mistakes to make me re-think what I was doing.
Nowadays, I'd advise a little of the same. Your biggest investment should be time spent learning and making friends. Then start by investing the minimal to get you started (unless you have 100sK).