I never wore make up in my life other than when in costume.My skin is thankful for it, too, I think.
I don't usually care how I look. I have sensory issues as many on the autism spectrum do, and I need to be comfortable. Especially when meeting people. I don't have a large choice of clothes either as it is hard to find something that's my size and not bothering me (material, cut, colors etc). I can't wear shoes or socks either and only wear sandals save in the deepest snow thanks to edemas. Gets me a few weird looks in colder weather.
I found at least half of my players in two of the groups have the same problems, husband included.
Yes, our society sucks in the way it cares about appearance, but at least the nerdier activities in this world should ignore that. There are other reasons for people not to need to care about how they look than supposed low self esteem or sloppiness. And I'm in anyone's face who dares to comment on my choice of attire if I happen to hear them. They are usually terribly embarrassed about it.
I insist on cleanliness and politeness with my groups and prefer non-smokers, but I don't care at all how people look other than that their clothes should fit and not expose too much of their anatomy, be that belly free on purpose or shirt too short
I also found that after a few sessions, people who first came in different clothes find it relaxing to dress like everyone else and not to care at all. With the exceptions of a few girls and one of the young men (who actually does show up in a suit but he has a reason for it).
It is possible that it has helped to put requirements like cleanliness, no smoking, no shouting in the house etc on the recruitment info. I have only once had to turn someone away for looking like he had fallen into a pot of grease or something. Of course, if that is the type of people who tend to show up I'd not want to game with them either.
Actually many studies have shown that wearing make up helps protect the skin from pollution. What is bad about wearing make up is not taking it off ans sleeping in it then just putting more on top. I have worn make up since I was 16 and I am now 54 and I have great skin.
You can wear make up and still look like a slob. What matters is how neat and groomed you look and if your outfit is appropriate for what you are doing.
You have a condition that makes it hard for you but I really doubt that all the rest of the nerds who dress like this have an autism disorder. My friends who dress like this do so because they don't care how they look because they feel that it does not matter because they are fat. That is very different than not being able to wear socks because of your autism.
And there is a difference between wearing a nerd shirt at a con or a game and wearing it out to dinner with the family or non nerds.
There are also causal woman's shirts cut like t shirts that are made in a variety of colors they just don't have any sayings on them which solve the comfort problem without screaming NERD.
I feel the same way about guys who wear sports t shirts everywhere.
Most of the guys who I game with wear t shirts and shorts for gaming some of the shirts have sayings on them some don't but they don't dress like this to go out to eat or on a date.
One of the things that I have seen with the t shirt crowd is holding on to a shirt that is faded and worn or one that is to big or to small. If this is going to be your outfit of choice at least make sure that they are not worn out and fit and that the rest of your clothes are neat and clean and that your hair is clean and groomed.
If I played at your table I would still wear what I wear gaming which is casual jeans and a top and yes my make up and my jewelry because that is what I find comfortable.
There is no need to hide your nerd hobbies but there also no need to advertise them everywhere you go either. And I think that is true of all hobbies.