Mosch,
I\'m not a pro painter by any stretch of the imagination, but i can give you a few tips from what i can see here.
To start with. Thin your paints

Someone was going to say it, so it may as well be me! It may take you two or more coats to get good coverage, but it is well worth it for the effect.
You seem to have some base colours down, but with this huge photo i\'m sure you can see where you have missed little bits and the metal / primier is showing through. The red of his trousers is a very nice even colour, but his flesh is a bit blotchy. Another thin coat of that colour may help that out. I\'m not sure what the flap things attached to his belt are, i would presume they are made of leather, or a laquered armour style like samurai. I would think about changing the colour so it wasn\'t the same as the belt. I haven\'t mentioned highlighting yet, but someone good at it will i\'m sure
Onto the metallics. Silver and gold look really plasticy if painted straight on. There are a number of ways you can change that. The easiest way is to base coat the silver areas black, and then drybrush silver over the top when it is dry. If you keep it light you can do it a few times until you are happy. The other way is to base coat it black, and then use very thin layers of silver. You may need several and it will look really grainy at first, but givews a nice effect. You can do the same with the browns and golds.
to achieve the cartoony effect, you could dd some darklining around all the edges with very thin paint or ink. This is difficult to do at first, but gets much easier with practice.
Second to finally, there are loads of brilliant articles on this site about painint techniques, have a browse.
Finally (at last i hear you shout!), practice, practice and maybe practice a bit more

I\'m a naff painter, and a very clumsy one at that (I have a habit of gluing myself to things!), but you can only get better if you practice!
Show us Randall when you have finished him, and i hope this helps a little.
Shaz