That's awesome! The thing that helps me most is tutorials so im going to recommend one here for you
How to Make an Icon
I think the colors and shades could be a bit better also, so I'd recommend using a similar icon to pick colors from and then adjusting them to taste. Let me know if you have any questions!
by the way, using the brush tool is probably the best way to get that "cartoonish" warcraft hand-drawn art style in my opinion but i've seen the dodge and burn tool implemented well before to make great results.