Hi, Seph!
This is a really nice painting, especially considering you've only been painting for a month! That's great! When I was your age, I was still scribbling ugly horses in the margins of my schoolbooks!
I think one of the things you should think about when painting is what colours you pick for shading. I see you've chosen to pick grey for the shadows on this one. This is fine in some cases, but it can make colours look a little washed out and boring. Especially when you're shading skin - the more grey you put on skin, the more your character ends up looking like a zombie! XD
You should try to experiment with using colours for shading. Put some blue on there, and blend it with the skin-tone, perhaps - or a bit of purple. Also, because skin is actually kind of translucent, it means that in certain areas, the blood below actually kind of shines through; usually where the skin is a bit thinner. Ears, for example, and the tip of the nose, and the lips.
But you should think about the colour of the shadows everywhere, not just on the skin. Light usually has a colour, which means that the shadows will too - if the light cast by your light-source is yellow, the shadows will look a bit purple. If the light is more orange, the shadows will look a bit more blue, and so on. Imagine you're outside on a sunny day, and you're wearing a white shirt - if you hold up your hand to block the sun, the shadow cast on your shirt will look a bit blue, instead of just grey. Using that kind of thinking when painting makes the colours look more realistic.
Also, as a last note - I don't know what program you're using to colour, but it looks like you're using the smudge-tool to blend the shadows. I would suggest avoiding this as much as possible: a little bit of smudging is fine, but a lot of shadows actually have hard edges, so if you blend every edge of every shadow, it ends up looking a bit muddy. Don't be afraid to use hard-edged shadows! It will help you practise the shapes of what you're colouring, so that when you shade it, you know where every shadow is supposed to go, and you'll avoid everything looking so flat.
