I'm not certain I follow you. The propellant you choose will dictate where to start, of course. Choose your maximum chamber pressure and begin at least 5% below that charge before working up. Some people will advise to begin 10% below charge, and with some propellants, that can be sage...
May God comfort you, your mom, and your sister. I know it will be a meaningful effort for you to get this rifle dialed in and using it to tag a fine whitetail this year.