With regards to gravity consistency, you could stick to the same water to grain ratio for every batch. For example: 1.25 qts. water to 1 lb. grain for the mash and 2 qts. water to 1 lb. grain for batch sparge for a total of 3.25 qts. per lb. of grain. If you increase the mash water qty., lower the sparge water qty. the same amount and vice versa.