mmmm...looks a bit just like a signature. The halo is dope. Try the tag with a marker instead of a pen so you don't get those super sharp edges. Also the D seems really wide and the other letters are a bit squished. I could give you an idea if ya want

 

make every letter more or less the same size and pay attention to letter spacing focus on the legibility and not if it looks graffiti enough or not style comes with practice

 

As a toy myself I would highly recomend doing it over and over till you get crazy and do it more till you know its good and also better markers help! Looks alright for the first though...