First, if I were you I would look at this thread as a "look what I did" more than asking for a critique. Which is a good thing. Your showing you can get something better than Halloween quality, but not break the bank or spend 5 years making it.
Now, as to how you can improve this for not much more money..
Go to a Goodwill or something and see if you can get some white pants to match your top. Then a $2 box of Rit to get it a very light gray. the pants are almost not noticeable, but with the spats, it stands out.
Play with your plate alignment. Raise the collar and the rest of the plates. Raise the shoulder bells too. (possibly free!)
Get a can of Ultra Flat Black spray paint and mist your plates and suit. Hit the lower legs, bottom of the cape and other random spots harder. Built it up to be darker gradually. ($4)
Buy a thicker and cut a shorter piece pf pipe for your rocket. It will look better than the thin one ($2)
If you have a Michaels, pick up some cheap doll hair, usually pre braided for Wookiee scalps. ($5 ish)
Perhaps attach a tube to your gaunts to greeb it up. ($2)
Check out batninja's belt tutorial on here. You can make an accurate Boba belt for less than $10. Using it as a guideline, you can made an approximation for as little as $5
I think doing those couple of little things would improve your look quiet a bit. If you had extra paint, respray all your armor silver, then use mustard or toothpaste to "paint" on spots where damage would be. Then spray the yellow on all of it. Wash off the mustard/toothpaste once the paint dries. Then re-add the masking (the mustard) to the now silver spots and then some more places that you want yellow to show through. Respray the green on the appropriate plates. See if you can pick up some Pumpkin Orange and slightly mist the right shoulder, just enough to change the color a bit. Then do the black misting for weather and finally a few coats of clear flat.
If you were brave and came into a spare 20-30 bucks, you could buy some sintra / foam pvc and make armor that really contours to your body and fits better (which is part of your collar issue). Its easy to work and cheap.
Overall though, great job!