There are a lot of different ways that people can experience attraction, and so there isn't necessarily one answer to this question. Some people might say that they are gay if they are attracted to trans women, because they are attracted to people who are the same gender as them. Others might say that they are straight if they are attracted to trans women, because they are attracted to people who are the opposite gender from them. And still others might say that they are bisexual or pansexual if they are attracted to trans women, because they are attracted to more than one gender.
So, what sexuality you are if you are attracted to trans women really depends on how you define your own sexuality. If you feel like you are only attracted to people who are the same gender as you, then you might identify as gay. If you feel like you are only attracted to people who are the opposite gender from you, then you might identify as straight. And if you feel like you are attracted to people of multiple genders, then you might identify as bisexual or pansexual.
It's also important to remember that sexuality is fluid, which means that people's attractions and orientations can change over time. So, if you find yourself attracted to trans women, it doesn't necessarily mean that you have to label yourself as anything in particular. You can just go with the flow and see how things develop.