DoL means Disciples of Land or a gathering class the other one you probably came across in DoW/M which means Disciples of War/Magic. I'd recommend having one Disciple of Land and one Disciple of War/Magic depending on your main fighting class say it be Paladin (gladiator) for example I'd choose for my retainer to be Paladin so for the most part the gear that I get from my main class when I our grow them I can just equip them to the retainer.