Parents Need to Celebrate, Not Tolerate, their Queer or Trans Child

Congratulate them on the internal work they've done to get to this point.
Thank them for telling you about their identity; coming out is a sign of trust and a willingness to be vulnerable with you.
Tell them that you love them exactly as they are.
Tell them that you love them because they're queer or trans, not in spite of it.
Tell them you will continue to love them as they grow further and further into themselves, including if they return to identifying as straight or cisgender.

7 Clothing Brands for Transgender Kids and Teens
Fit4U Solutions
LeoLines
Sock Drawer Heroes: Dedicated to Gender Euphoria
Tuck Buddies
Your local thrift store with a decently large selection of clothing for your young person to choose among.
Another idea is to have a birthday party with a clothing swap instead of gifts. This could be tons of fun, not to mention that it may get rid of stuff that's not being used (albeit only to be replaced by other stuff). And it's certainly more economical and easier on the planet than buying new gifts.

Note that some of the things on this page may be challenging (or impossible) if you're foster parenting a queer or trans young person.

See the parenting books in the resources section for additional suggestions of ways to celebrate your child.

"Mostly they just say that they love me anyway. Which for me is a bit of a sting, because I don't want to be loved 'anyway'; I want to be loved FOR who I am, not DESPITE who I am."

"My Jewishness is part of my queerness and my queerness is Jewish and they are both a part of me and queer Jews have always existed."