Hello Zubamse,
Welcome to the forum.
The space should 0.2-0.5, depends on your print setting. If you use raft you can have bigger space, if you use no raft the space need to be smaller in order to get good adhesion to platform. The nozzle height value determine the space, you can do some small test prints, to adjust nozzle height value manually to optimal before going real.
We suggest use raft as it increase print success rate. The coating may have shallow marks after printing, it does not mean they are destroyed, it is quite durable actually.