Lots of good advice so far. When I first decided to start dressing better, I realized I wanted to be perceived as a competent, mature adult. I couldn't do that in ratty t-shirts and cargo shorts. So, I started wearing things like khaki chinos, leather footwear, oxford shirts, sweaters, and sport coats. Decide what you want to "say" to the world. Also, actually live your life. Clothes are not the endgame. They are the tools we use on the adventures of life. If you actually are living a full life, your style will naturally flow from that. Don't spend all your time looking at instagram and wondering why your style doesn't feel like "you". Get off the internet and go live life and your style will follow.

I went from sweatpants/hoodie to above average for men (but definitely far from 'fashionable' for the most part) a few years ago. The biggest thing is just making sure what you wear fits properly. The second biggest thing is only get a few new things at a time. If something is a completely different style than what you are used to, you don't want to completely fill your wardrobe with it overnight. This especially sucks if you end up not even liking the style. Get a few pieces or just one whole outfit, wear it on days you're feeling confident or just days you don't leave the house so you can get used to it without the social pressure you are feeling. Trying too hard only really happens if you wear a suit to your new job at McDonald's. It's all dependent on social setting, and if something is considered formal wear, for the most part. It also can happen if you are surrounded with a bunch of people who don't care and have the mentality of crabs in a bucket, pulling each other down when one tries to leave.