How can I improve from this?

[Gabster]

Hey! I'd done this painting as part of a fun little art trade with another person on DeviantART, but the more I look at it the more I hate it.

http://fc07.deviantart.net/fs70/i/2012/2...5e03sd.jpg

I can already see the big problems really - poor composition, muddy values and all that but I cannot for the life of me figure out how I can fix these issues in future. I just keep making the same mistakes, over and over, despite trying to force myself not to.

I was hoping one of you wonderful people would be able to point me in the right direction. (:

(Also just occurred to me this might be in the wrong area on the forum. Sorry, it I've messed up!)

[Frankie]

You can start improving by using only one brush for your next painting. Maybe 2.

[Gabster]

I'll get painting right away, and this time, no abusing the custom brushes, ha. Thank you, Frankie! c: