1 litre sized pot.  Lysimachia nummularia "Aurea" is an eye-catching ground cover that has bright lime-yellow leaves that are bright yellow in response to greater sunlight and has yellow flowers in spring/summer.  It prefers moist soil, tolerating quite wet conditions.  Can look great hanging over pots, banks or for providing colour under shrubs.  I grow it among ajuga with its purple leaves for an awesome contrast.  It is a ground cover so will spread along but is not invasive and easy to remove wandering tendrils that appear where they are not wanted.