Nothing done wrong as far as I'm concerned.
Hmm, neat fig. The sharpie work is somewhat messy, but rather good-looking to my eye nevertheless. The silvery daggers look particularly nice.
To improve it, I'd suggest taking a fine-pointed marker and and trying to draw some relatively clean and smooth outlines to the belts and daggers. That'd make the fig look more solid and LEGO-like, I think. That would give a chance to smoothen the sharpie work, too, as fine markers are more easily controlled. You could also draw some detailing on the hood, like the seam patterns shown in the reference picture.
In addition, I'd also suggest giving the fig black legs and making him a skirt of white paper. That would look more accurate and give more room for detailing. A skirt model shouldn't be too hard to make, but there are most likely loads of ready design floating around in the internet, too.
That's my 0,02 €.
