Your place of employment may already include staff of your own gender, and you can be guided by their dress code, which will exist whether official or not. Traditionally people tend to wear smart clothes to the office, whereas practical work necessitates practical clothes. For the ladies, separates are more practical than dresses in most situations. You can ring the changes without looking like a fashion victim, besides it gets expensive if you wear dresses because every time you spill something the whole outfit goes in the wash. Don't be afraid of a splash of colour now and then.
Shoes are of paramount importance.
Go for comfort not just style, as you will be wearing them all day. If you like short Skirts be sure you can sit in them without revealing all to the world. Remember a shapely leg can be shown off with a back slit in longer skirts, so you don't need to cover your assets entirely. We all operate within unseen social boundaries, it is not until we start crossing them that they sometimes come up and hit us in unexpected places. Your gender identity is the very reason that you are undergoing treatment in the first place.