First, read genderfic. There is a lot of it, some good and some bad. If you like fanfic, check out all the lovely genderbending stories out there. Out of my own projects, I recommend "The Hawkeye Initiative," Frankenstein's Family, Schrodinger's Heroes and The Ursulan Cycle.
For original work, consider fiction and nonfiction about transgender or other gender-variant folks. Science fiction contains many stories that explore alien sex/gender dynamics. Out of my own work, I recommend An Army of One, Calliope, Kung Fu Robots, The Steamsmith, and The Blueshift Troupers.
When you start writing, it's easier to start small. Drabbles or short stories are great choices. So is narrative poetry. allbingo has monthly fests and a bingo card generator; you could make a card of gender motifs or short-writing prompts. For January 2018, our theme is Apocalypse, but I'll run Valentines Day in February (with platonic and romantic options) which is a great match for genderfic.
It's also easier to start close to what you already know. Female writers portray men, and male writers portray women, and if you take a closer look at what womanhood or manhood means to you or your characters, it can be pretty awesome.
Check your circle of friends. People often know someone who is trans or genderqueer, etc. They can help you get a feel for those characters. Ask them what they're sick of seeing in entertainment. Don't write more of that. Ask them what they want to see that they're not getting enough of. Write that. If you invite feedback from your friends, you will improve faster.
Watch out for stop-tropes. "Trans prostitute" is a good example, and most fans are already familiar with "dead/evil lesbian." Here's a whole list of problematic portrayals. These are traps a novice would do well to avoid, and should be handled with care even by experts -- you have to justify the risk the readers are taking by reading something so fraught. Search "trans bingo" and you find examples like this to avoid.
Make friends with other folks who study gender and/or write genderfic. I have lots in my audience because I write it all the time and it attracts people who read those things.
What are some of your favorite sex/gender resources?