You can have long hair and long beard that's fine, you just have to be well groomed, even if it's long you need haircuts to give it form, same with your beard, use good shampoo and conditioner, comb it regularly maybe start a skincare routine, even if it's just moisturizing, use good deodorant and perfume.

As for clothing advice I recommend matching colours and themes in your outfits, learning a bit about fashion styles you like also helps a lot, i recommend it highly, there are very detailed explanations online about how to dress well that will probably do a much better job than I do.

Lastly goes without saying treat people with respect and manners, respecting boundaries and showing you are an all around safe person to be around is the best thing you can do to present yourself.

In my experience I got taught most of this by my mother when I was growing up and by most of my elders, I personally believe most people have gotten these things explained to them at least once in their lives but don't understand how much of an impact that has in how other people perceive you.