Relief, then action, then intonation.

Neck relief sets the curve under string tension. Action sets string height. Intonation sets speaking length at the saddle. Change relief after setting intonation and the intonation is wrong again.

Measure relief at the eighth fret with the first fret fretted and the string pressed at the body join. Measure action at the twelfth. Set intonation last, and check it at both the twelfth fret harmonic and the fretted note.

There is no universal number. There is a sequence — and doing it out of sequence is the most common reason a guitar "will not stay in tune".