Richard what is meant by saying "buy your way into social circles" is this:
You can pay to be a member of certain organizations or you can pay for things that give you entree into social circles you otherwise wouldn't have had access to previously. For example, if you join an exclusive and expensive health club (there is one near me that runs $175/month for an individual - family memberships are much higher) you'll be moving in more successful social circles JUST by joining that club. So other people you meet and chat with in that club are going to be more affluent rather than less. Often times these type clubs have social calendars and as a member you are included and invited to various events. People who can't afford the cost of the membership are generally not going to be present, so you'll be moving in circles with a wealthier group of folks. These folks will also be MORE INFLUENTIAL as a group than the general population so they are good to know.
Another example would be becoming an art patron or a theater patron or becoming a donor to a charity that you want to assist. In buying art from higher end galleries, or going to the theater regularly (or becoming a donor) or benefiting a charity you'll meet other people who have money because these are things people with money do. You'll be invited to various events thanks to your purchase and/or your patronage and this does have social benefits.
Finally you can do this by frequenting high end venues (the expensive steakhouse with the swanky lounge/bar area for example). You go there to eat, but if you sit at the bar and chat to other diners, you'll be chatting to other people who can afford and choose to eat in an exclusive or expensive venue.
So you are buying your way in, but indirectly if that makes sense. You aren't paying to play with the cool kids, except you ARE, it's just you are paying for a piece of art or a club membership and the social advantages are a side effect.