Coleus is the best bang for your buck at your local garden center.
You can pinch it off or cut it off when it gets tall and leggy. Then you can stick in the ground or in some water and root some more. It grows very well in the shade or partial sun.
It is the plant that keeps on going for the long haul one 6 inch pot can turn into 20 very quickly. It comes in all colors I love them all and have most of them in our yard and in pots.
See the tiny little one that one we discovered earlier this year at Lowes and that was three 4 – inch pots that made that amount.