Absolutely 'ideal' (but rarer than hen's teeth
in workers) is FN, PRA, hip scored and elbow scored parents. What are you wanting the dog for - pet, agility/Flyball or gundog (working dog and or trials)?
Breeders breeding for agility seem to be hip scoring more, whereas you'll have a bit of a battle finding trialling stock with all of the above screening, and of both parents. Quite a few working stud dogs have now been screened for PRA, but FN testing is less common and hip/elbow scoring still even less common in trialling stock.
I'd have a look at articles on hereditary conditions so you understand how conditions are passed on, and decide then what you are happy to accept (or not) as far as testing is concerned.
Good luck with your search