A bag of coffee has about fifteen brews in it, and the first three are for learning. Here is the quickest way to spend them.
Brew one: make it exactly as the bag says, 60 g per litre, and time it. If it took much less than three minutes the grind is too coarse; much more and it is too fine. Write down what happened.
Brew two: change the grind and nothing else. Finer if it tasted thin, sour or salty. Coarser if it tasted bitter, dry or dull. One change, one brew.
Brew three: now change the ratio, not the grind. More coffee if it still tastes weak, less if it is heavy. By the fourth cup you are drinking rather than measuring, which is the point.