Do as the title says! Choose a pokemon that feels close to your gender, or just a pokemon that you vibe with. Concept inspired from a dream I had about Hexbear talking about pokemon cards as genders. Also Estradoll was there

If you don't have a specific pokemon you can decide on, there is a fangame called Pokemon Infinite Fusion where you can fuse two pokemon, and there is a ton of different sprites for it. You can look at them here: https://www.fusiondex.org/

Choosing the trans girl favorite of Sylveon for myself, because trans colors are sick as hell, fairy types are cool, and also am puppy/catgirl.

If I were to choose a fusion favorite, I'd choose this:

https://www.fusiondex.org/339.288/ Its a hybrid of Gallade and Sylveon, and it hits me in my heart of being trans colors and reminds me how much I love strong women. There is also a magical girl version that is also cute as hell

I also found one that's a hybrid of Zoroark and Misdreavus while looking for one for Estradoll and am adding it to my list https://www.fusiondex.org/200.338/