Imagine a race between a rabbit and a tortoise. The tortoise plods along in a straight line, but the rabbit is so fast, it can afford to taunt the tortoise by running in circles around it, covering far more ground, but still crossing the finish line first.

By extension, "to run circles around someone" or to "run rings around someone" is to outclass or outwit someone very easily.

The writer has just changed "run" to "sell", knowing that the reader will recognise the idiom and make sense of the expression. To "sell circles around people like me" means "to outsell me"; "to sell a great deal more than me without much effort".

Personally, I don't think it is a very good adaption of the expression, but others may disagree.