I bought a 3 gallon kegging system from rebel brewer. it doesnt have a co2 tank or regulator. i plan on naturally carbing it for the first few brews untill i can buy the co2 set up. i dont know anything about this and the info i have read is a little confusing. will i need to purge? how do i calculate priming sugar (i know its not the same as bottles)? what should i know before attempting this? sorry for the irritating questions and thanks for your advice.