riccia needs a good flow across it to grow, its a heavy feader, taking in huge amounts of phosphates and nitrates so long as it has enough CO2 to drive its growth. Dont forget it doesnt have any kind of root system, so itll need to be netted down.
As far as your other plants intake is concerned, itll take a few days for your plants to wake up and start feeding. This is the most important time for you to get your CO2 right, if you dont have enough CO2, your plants arent going to take up anything at all, as its the availability of CO2 that allows your plants to feed in the first place.
If you need a neat way of stopping it moving about, make a lassoo out of silicon tubing, block off both ends so it wont sink. You can glue it into a lassoo leaving a tail on one end of the circle, this tail you can then anchor to the side of the tank where you want the riccia to be, then place the riccia inside the lassoo, so long as its not got a huge current going under it, it should stay in place very nicely as any surface movement will be prevented by the tubing.
Once your CO2 is good, and your ferts are good, then your Riccia will pearl like a crazy thing after about 2 hours of light, less in high (3wpg) light situations. If its not, then somehting is still way out. Go over everything again, if your dosing EI, then you can ignore all ferts and it MUST be your CO2. If your dosing as much CO2 as your fish will allow you, and its still not enough, then you need more surface movement.. aim a power head up slightly until you get your skimmer.