I like to keep phosphate at 0.05ppm (0.03 is considered ideal by many but check your specific hanna checker to make sure there is a realistic error range to maintain 0.03). 0.05ppm gives me some flexibility with testing errors and needing to dose.
For nitrate, 5-15 is common. I like to stay at about 10 ish.
If you feed heavily the right foods that corals will use, you can keep very low numbers. This however is not very popular as very low numbers are hard to maintain