The biggest advice I can give you is, you need to try to be social. It’s easy to hang out with friends in high school because everyone’s locked into the same building every weekday for 6 hours.
Once you’re an adult, you no longer have that limitation. Even college is more of a “go to class for 2 hours a day then leave afterwards” type of experience. It’s certainly liberating to not be forced to be someplace for long periods of time, but it also means that the primary reason that you hang out with your friends (ie, because they’re already there with you) is now gone. It can make for a very lonely experience.
You need to go out of your way and actively maintain your friendships. Make plans to meet up at least once a week or something. Otherwise, you won’t really get another chance to make deep friendships
I like making costumes! If anything, it’s a good way of making clothes that you would never make otherwise, and there isn’t anywhere near an expectation of quality. Making a costume yourself basically automatically ensures that people would be impressed, no matter how shitty the costume is.
Regarding perfectionism, it’s something that I’ve had to learn throughout my various forays into arts - there’s going to be mistakes. There’s always going to be mistakes. You can’t avoid it, no matter how skilled you are. The skilled artists know how to avoid drawing attention to their mistakes, and that generally means that they just let it happen without caring about it. But also, it’s just a costume, and as mentioned above, people will be impressed regardless of how shitty it is.
Regarding effort, it requires a lot of effort. Because you’re making unusual clothes, you need to spend a lot of time to design it and make sure it fits properly. I designed costumes this year for me and my partner, and in total that took maybe 2 months. It’s also more expensive than costumes you buy online. The raw material (cloth, thread) was maybe around 200 USD total, roughly 4-5x the cost of a regular costume you can buy online, or 2x the cost of a niche costume that you can buy online. It’s definitely not a good use of money and time, but it’s a good hobby project.
Regardless of if you buy a costume or if you make one, here’s the trick: don’t skimp out on the wig. Most people don’t wear a wig, and the people who do tend to use cheap wigs. Cheap wigs have a plastic-y texture and are difficult to style. I get wigs from Epic Cosplay, which have a lot of different colors to choose from and tend to look fairly realistic.
Also, wigs never come with hair already at the right length! Make sure to give the wig a haircut, it’ll look way better if you remember