One of the first steps, or for some, the last, is what order (aka color scheme) you are going to use and if it is one you've created. This is the background, history, and most importantly, what paints you are going to have to buy. You can choose one of your own and make up your own history, etc and choose your own paint scheme or choose one of the established orders below.
There are six established Orders by Games Workshop (as of the 2nd edition codex), three in each Convent. All use three colors, black (chaos black), red (blood red) & white (skull white). (You may also want to pick up some bolt gun metal color)
Convent Sanctorum Based out of Ophelia VII
Convent Priors Based out of Terra
All of the images that the above link to are copyright, trademark, etc. by Games Workshop. I use them without permission. They are scanned from the Sisters of Battle - Warriors of Redemption pamphlet.
