Time. Hair removal. A more flattering hairstyle. A skincare routine. Better fitting clothes. Glasses that frame your face better. Shaping your brows a little more. Get more cardio in (dancing is a good way).
All of those will have an effect, and you can pick and choose whatever feels more appropriate for you. You've got time to figure out where you are most comfortable, and what you want to present yourself as. Create a Pinterest with all the looks that you gravitate towards, and start to find ways to incorporate those elements into your day to day.
What would be more flattering honestly, I can never get a clear answer. Also sadly I can't really try out hair styles since straightening it would be semi permanent.
The photos look like there might be a decent amount of frizz and/or you might need to trim a half inch due to the ends. That could be lighting or it could be a little on the dry side. If you aren't already using them, it might be worth looking into a wide tooth comb and some argan oil plus wrapping it at night. Honestly I'd suggest considering going a little shorter than you have it now, like just barely longer than chin length. Don't straighten it! But do look into hairstyles that you like!
Your curls are beautiful, but managing them is hard. It takes a while to find out which products work, so you could experiment a bit. It looks like you currently don’t have any layers in your hair, which makes the style look a bit bland. Going to a hairdresser and getting some proper layers would probably do wonders. And as someone else said, a ponytail with your hair would look really nice.
For real you have glorious hair. Like take one big handful of it... that's more than all the hair on my head combined.
There's a lot of potential there.
I also part my hair in the middle by nature, with it falling equally on both sides. I found that I can achieve some really interesting, different looks by side parting, and optionally pinning back the side. Kind of a variation on an "undercut" but I don't really wanna shave off my hair! Braiding seems to be the "trendy" way to do this, but idk how to braid my hair yet.
You could get some hair ties and experiment with pony tail(s) and partitioning your hair in interesting ways. The way I look at this, there are no rules actually when it comes to your style. How people create new trends is just that, breaking existing rules. Goth can overlap with many other styles, western, punk, cyber, industrial, even pastel goths are a thing!
I think the main difference between your selfies is in #1 you are looking down at the camera, in #2 you are looking up. Perspective difference changes the perceived shape of your face. I'm exactly the same way; my favorite selfies are at an angle from above. In fact that's a super common way to take selfies if you ever notice.
Now, why does that matter?
No seriously lol. Why does it matter how you look in selfies. Honey you wanna be your gorgeous self all the time. Nobody is going to see you as a selfie, except on the internet.
So get yourself a lighted vanity if you don't already have one. Put it somewhere comfortable and take a seat (mine is on the kitchen table). This is how you're going to work on your look.
I have had tremendous success with eyeliner. You want a goth look? Eye makeup is a big key to that. My partner gave me their "pencil" which is actually like a cream or something but in shape of a pencil. This tutorial helped me greatly:
https://www.wikihow.com/Apply-Eyeliner
As you can see, there are many different types of eyeliner. You don't need anything super fancy or expensive to start.
The other key part is lipstick, dark colors are kinda standard for goth looks. I got a dark purple which is OK... but I think I'll pick a more neutral color next time.
In fact I got a cheap "all-in-one" makeup set with gel eyeliner, blush, eye shadow and lip tint in it. None of it is great, but perfect for learning technique and finding your best colors! I brought my own brush set, a good set helps.
other basic supplies you need: cotton balls, makeup remover wipes, q-tips.
I'd work on setting up the photography. The second photo definitely looks better because of the higher camera angle, but the pose, lighting, focus, etc. could all be improved.
I'd suggest looking up a few blog posts on how to pose for selfies - it makes a huge difference, and take the photo somewhere where the lighting's naturally right rather than wherever you happen to be. Use the timer function so you don't have to hold the phone, and take loads of photos so you can keep the best and throw the rest away.
And remember - the good photos are what you look like in real life, the bad ones make everyone look terrible. It'll make you look gorgeous.