If you're going for a bit more of a cartoon-ish style, then I think you're doing quite well. Try adding some more leaf volume, as the tree looks like it's a bit low on leaves.
However, if you're going for a more realistic or semi-realistic look, then I have some more to point out. The trunk feels a bit unnatural, because it's perfectly straight and vertical, and at the base it curves out with a perfect slope. Trees rarely do that in real life. Look up a few references and see how the trunks of trees bend and curve and thicken near the bottom, as well as how their roots meet the ground.
The trunk also looks quite thick, especially for the volume of leaves you've drawn. Try making it a bit thinner and, as I mentioned, adding more leaf volume. Lastly, making the outlines of the leaves more jagged and random will help make them look more... leafy?
That's all I've got to say. I think you've got a great start!