What kind of stitch do you use to determine gauge?
Patterns will tell you what stitch. Often it is stockinette stitch, but not always. Sometimes there is a specific stitch pattern that they want you to use. Just look in the GAUGE part of the pattern and it will tell you.
If you’re trying to get the gauge that’s on the pattern label, it’s stockinette. However, that’s not as important as a pattern gauge. Label gauges are more for determining the `weight’ of a yarn, as in - worsted, DK, sport, fingering, etc. It’s the pattern gauges you want to try to get and each pattern is different - even with the same yarn.