First thing you will need is the Codex for your army which is a book supplement that gives you all the info you need to play and build the army as well as extra lore. The codex you will need is Codex: Adepta Sororitas.The Start Collecting/Combat Patrol boxes are a great choice to start your army because they save you a better amount of money than if you bought the contents separately. Cool units you can buy for the Adepta Sororitas in addition are: Seraphim Squads, Paragon Warsuits, and the Immolator, to name a few!