Hi Wudy,
The usual method of propagating Gypsophila is by seed which can be sown in the early autumn or mid spring.
They do not take well to transplanting, so it's best to sow the seed in situ either in shalow drills or just scatter them and cover lightly with soil.
They are a little tender, so if you sow this autumn it's best to keep them covered with a cloche for witer frost protection.
If you push some twigs into the soil, this will remind you where they are and also provide something for the plants to scramble through as they grow. Good Luck. Tbird+