Well, first of all you need to know anatomy of ponies. Tutorials [link][link] will help you. And then, try to make rubbings from other completed drawing (you can use mine, for example), or from the show. I believe in you!
Well I was trying to go more for the Sonic reference than the Pokémon reference since it fit more with the picture. Otherwise I would have done this: Twilight Sparkle is evolving. Congratulations, your Twilight Sparkle evolved into a Rapisparkle!
Yeah, as you can tell by my signature, I like a lot of thing. Kingdom Hearts is just one of those many things.
Twilight's cutie mark is a central spark surrounded by five others (like the five other main characters/Element bearers). And given that her Element is magic and friendship is magic, she essentially already represents both unity and friendship.