It depends on how much sun/shade/wind the area gets. It also depends where you live - certain plants will survive better in some areas than in others.
e.g. if you live in the south of England you might not be able to grow the same as in the north of Scotland.
It also depends what sort of thing you like and what effect you hope to have.

If you gave a few more details maybe someone will be able to help you.

And do you want to fill the circles with eg a small shrub or do you want flowers? Do you want permanent plantings or do you prefer to put in summer bedding and bulbs as the seasons change? Do you want to care for it regularly or for it to more or less look after itself with occasional care?

The actual size of the circles would be useful to know, along with all the other points raised already.

Ornamental grasses can look very stylish in stones, particularly Imperata (Japanese blood grass); also Hakonechloa Aurea and Carex Frosted Curls.