Rolling circles are easy once you get the timing down and they make people stop and look not to mention that they are a good way to work ailerons , rudder and elevator together in time with each other. I do them with my simple avistar trainer/sport. so you don't need some high dollar aircraft to do them and make them look good.
Maybe I set goals to high for myself, or maybe that could be why I am as good of a flier as I am. "not to ring my own bell" I worked all summer my second year of flying to do these, cuban 8s and humptybumps took me about a month each.
slow and smooth, that is the way to do it