Congratulations!
I second the point re suits, lots of suits look cheap, even if they're not. Bizarrely a nice jacket with non matching but toning dress / skirt / well cut trousers looks much better.
Dresses / skirts should finish on or just above your knee. More than an inch of thigh is not helpful if you want to be taken seriously.
Wear decent tights and think about your bra, no straps on show, smooth cups. In the summer, think carefully about wearing sleeveless dresses. Michelle Obama does it well, but in some offices it would be inappropriate. And definitely a no if the top / dress has deodorant marks.
Zara, Warehouse, Oasis and Boden all have good work stuff.
You should keep the following in your drawer: emergency new/clean tights, nail file, mouthwash, baby wipes, concealer and painkillers.
I also agree with the point re: iPad & keyboard in a big handbag. The LK Bennett Rosamund, Modalu Pippa or something of that size would work.
Well done. Now go show the men how it's done.