What is good glucose level?

Normal is good. If your blood sugar is in the normal range it is "good". Normal blood sugar is <110; a better test is a1c, which should be <6%.
It depends. In general, for someone without diabetes, a normal sugar, or glucose, level is 65-99. For someone with diabetes, a typical target range might be 80-120. However, for many people with diabetes, there might be reasons to have a different target range.