There is a formula you can use. I forget how it goes.
A roundabout method is to calculate an RC time constant that will yield a certain amount of ripple between crests.
For instance, if you want .01 V ripple, then volt level is permitted to fall that amount during .58 nSec between peaks.
The time constant is for a 63 percent change. This means your time constant will be 63 * .58 nSec (the curve isn't straight, but this should be good enough)...
equals 36 nSec.
Divide by your load, 1000 ohms (per your schematic). This yields a capacitor value of 36 pF.
You'll get better than .01V ripple since the waveform is not a void between peaks.