Both options are OK depending on what interests you more. I bid on Pricebenders more and sometimes play Eager Zebra.
Doing this, I achieve points and make progress both ways. You should not ignore any option in SFI because they are all designed to help you achieve success.
Start with the ones that interests you but learn others too and use them to your advantage.
Your SFI Business will grow gradually. It is good that you agree is a business.