In summary, to make money money on Betfair you MUST do two things. First, suck up every bit of knowledge that is available. Build up a small list of 'edges' to deploy when the time is right, understand that each of them has their place. However, the Betfair markets dictate when you will be able to use them.
To opt into paying just 2% commission, simply visit the 'My Account' section of your Betfair account and select the 'Basic' rewards plan. The 2% commission rate will be applied to your account immediately and you can start making those commission savings.