1st. If you have an idea, but you don’t think you can do it: Do it anyway! You won’t get anywhere if you don’t try and keep trying!
2nd. Start learning basic anatomy. Its boring, tedious, hard and frustruating, but trust me it helps…. A LOT!
3rd. The reason everyone can draw a character is because they’ve caught their characteristics. With Rythian; he’s a mage, wears a purple scarf, brown hair with a lighter hair tip and glowing lightblue eyes. BAM! Rythian.
Duncan: blond, always wear goggles, a white science coat and gloves. Done! You have Rythian and Duncan, no matter how good you are.
What improves your drawing is simply practice, there are no tricks to it. And if there were, you’ll have to master the basics before using the tricks: A wizard can’t start casting fire before casting water; otherwise his house would burn down…. you know?
Take one step at a time: Faces, bodies, then arms and legs.
Take it easy.
I hope that answers your question.