what else can I do apart from be a good parent?
If you have a daughter, let her have whatever tomboyish interests she might have, let her wear "boys'" clothes, let her cut her hair and go run outside in the mud, encourage her to pursue her interests in the sciences if that's her thing, a lot of the old fashioned dysphoria seems to come from GNC (tomboys/effeminate boys) children not being allowed to explore their interests fully. Also, keep her safe from sexual predators, pornography, and the dicks who will tell her that her only value as a woman is looking attractive and that she's inherently less valuable or competent, due to her sex.
Same goes for if you have a son, let him play with dolls, paint his nails, and grow his hair, and don't punish him for being emotional or sensitive.
With all the trans people I've spoken to over the years, the common thread for men and women is that the boys tend to be punished severely for being emotionally sensitive ("boys don't cry", and so forth), and liking traditionally "girly" things, and the girls tend to be tomboys or butches who are denied the ability to explore their interests and envy boys for being able to do the same, and are later sexualised and dehumanised too early. Sexual abuse or exposure to a BPD or narcissistic family member will also increase the chances of your kid becoming trans.
Basically, just explain that men and women (and girls and boys) are all just human at the end of the day, and you can have whatever career, interests, and personality you like, even if it doesn't conform to sex stereotypes/gender roles.
You're right to some degree but dress wearing? Nah, that's a line crosser. We have different clothes for different sexes for a reason.
If he wants a stuffed bear or she wants an army figurine that's fine though.
My childhood best friend used to wear my princess dresses and fairy wings, and push around a baby doll in a pram, when we were kids. When you're like 4-8 years old it doesn't really matter, you're just playing dress-up. He turned out a regular heterosexual man, for the record.