Here is the first one I sewed. I sewed this one shortly after, making some alterations. I thought the sleeves would be cute with gathers, and I changed the rounded peter pan collar to a pointed style peter pan (or, flat pointed, I think they are called).
First, this just shows the bust adjustment i made, taking up the extra slack in the side bust dart. I didn't need to make the whole thing wider, as most FBAs show you to. I don't know if this is proper, but it's what I did.
Then I made a simple sleeve cuff, cutting a 4" wide strip, by the circumference of my upper arm. I wanted it snug, but not tight. Iron the piece lengthwise in half, and then turn in each outside length towards the middle, and iron again. Sew your piece together, at each end, making a ring. For the sleeves, I just altered the pattern by adding more length at the shoulder line of the sleeve, ie. a bigger curve at the top of the shoulder, and a wider circumference at the hem of the sleeve.. I sewed a practice to get the angles right. Sew long stitches in the cuff part of the sleeve inside your seam allowance to gather later.
I attached the cuff, right sides together, and pulled up the gathers in my sleeve to fit the cuff.
Sew the seam of the cuff to the sleeve along the line you ironed, and then turn your cuff back the right way,
Then I top stitched the cuff in place, catching the inner fold of the cuff (so i didn't need to hand stitch it in place.)