To purchase 2 ft² will be quite costly. When I purchased my riccia initially from Xian Leng, it was on a mesh that was probably about 6 in by 6 in. I can't quite remember but I think it was for about RM 7. I had a single 15 W bulb then. I did not manage to get it to pearl until I had two 36 W bulbs going...

Once riccia pearls, it will grow very fast. If you don't trim often, the bottom parts where it is attached to the mesh will not get much light and hence will disintegrate, making the riccia on top float since there is no longer anything holding it down. The parts that you trim regularly can be used to 'seed' another mesh.

Inevitably, some bits of riccia will find its way to the surface of the water. Since this is the brightest part of the tank, these riccia bits will multiply like crazy too. So, given the right conditions (mainly high light and CO2 supplementation), it is very easy to cultivate riccia.