I taught my undergraduate students as an openly transgender woman this semester, but on the first day, I wasn't brave enough to teach as a woman. I came out the next session, and only began dressing unambiguously from the third session onwards.
Because I had transitioned slowly in how I appeared in my students' mind from day one, I decided to do the same with my wardrobe. I wore androgynous clothing at first, then neutral makeup with androgynous clothing, then slightly more noticeable makeup with a woman's pants/top combination, then finally a skirt and pink woman's top, etc. I felt that going too big all at once might cause some issues; if nothing else, I knew I would be able to tell anyone that asked about me suddenly wearing red lipstick and a skirt that I had been presenting as a woman for a few days now, but they simply hadn't been paying sufficient attention.
I feel like a pants suit or something subtler is better for day one, and then you can go big on day two or three with something like a dress or pencil skirt--the things you mentioned. There's no one way you have to dress on day one, but it sounds like you've been doing something like what I did in my first few days as an 'out' teacher, and so going a little slower at first might be your best bet.
Hope it goes well! I'm excited for you!
