This is admittedly an excellent artwork for a first attempt! Keep it up
My tips:
1. Try a smoother brush for the lineart, because jagged edges are unfortunately very noticeable. Try zooming in more and drawing the lines that way, and that can help smooth them too. It can also be good to make a rough sketch before, especially for intricate details, which is what I do now.
2. Try exploring different color regimes. I can name many, e.g Gradient, flat colour etc. This in itself can give your drawing a more unique feel. I myself use flat colour on most parts, but for things like flames I use both gradients and flat, to make it more dynamic. Test some out, and see what works best for you.
3. Shading. Shading is very useful to make your drawing look good. It can show light sources, make areas 3d and even help recolour the image. I use adjustment layers for shading now, but there are a huge variety of ways to choose, e.g cel shading (often used in manga), soft shading (more realistic), flat shading (finsgraphics old method) etc. I think shading is really important to make your sketch look better. Highlights and rim lighting can also help considerably to show where light is most. Search for tutorials on YouTube/google if you're having shading trouble.
4. I have recently discovered. Albeit mildly advanced, it really does change an image. It can change a skeletons bone texture, add cracks to walls etc. Try searching it up on google, it can be very fun to play around with.
Anyway, excellent stuff, keep it up! If you need anymore tips I may be able to name a few
