I transitioned on the job after having worked at the same location for 20 years. I didn't want to overwhelm people with my transition, so kept my clothing very conservative at the beginning. It was easily a year before I wore my first dress to work, staying with slacks and at the most, capris and shorts.
Two years later, I changed jobs to one where I needed to dress more professionally. It's been a good experience to have the full wardrobe available without having people's historical memories to deal with.
I'm in the process of changing jobs again, and I notice that employees under my new employer dress much more conservatively. It will be another clothing transition, I believe.
My advice to you is to gauge your acceptance. If you think that there won't be any push-back when you transition, then open up your wardrobe to everything that's available. If you anticipate any non-acceptance, then dressing conservatively is a better way to avoid difficulty.