I have just completed two cotton lawn tunics from
Simplicity 1461 which I can highly recommend. It comes with multiple cup sizes to choose from.
I made the View D which is the most simple. I am now working on the View E.
Cotton lawn is a great beginner fabric. Works well for this style of tunic, presses easily, handles easily.
You could make one and finish the seams with a zig zag, then try french seams for the second.
Here it is on me, I'm a 24. It's slightly the wrong size for me (shoulder-wise) but I'm still happy.
Here it is on my Mum who is a size 24. The first version used the C-cup. I went up to the D cup for the second one. I also capped the sleeves on the second one as I felt there was too much poof in the first sleeve: