Sure, you can go and get all sorts of nice make-up, but I always find the cheap grease make-up to do the best, especially for around the eyes. Most Halloween make-up kits come with those black crayon-type things but they never go on very thick. The grease make-up goes on thick and easy. The only down side is that it never seems to dry so you might end up with some white make-up rubbing off on the collar of your shirt.
For the green hair, you can't go wrong with the cheap green hair spray. The only problem with that is that it hardens the hell out of your hair. If you want something a bit looser or more flowing, you might have to use a "semi-permanent" dye that you can probably pick up at Hot Topic.
Now, the outfit is going to be the tricky part. I doubt you will be able to find it for very cheap and most definitely won't be able to pick it up all together. You'll have to buy the purple, pin-striped suit separate from everything else. The shirt would probably be easiest to just buy an orange button-up dress shirt and sew an extra row of buttons on the front for the look. Finding a green tie shouldn't be too hard to find.
You're making a smart move by starting to get it all together this early. It'll take some time and don't be shy to experiment with the make-up before hand. Get it on good.
PS. Here's a suit. Like I said, this will be the most expensive part. Just check thrift shops often for a cheaper solution. You just have to be more flexible if you go that way.
http://www.ebay.com/itm/New-NWT-Zoot...#ht_500wt_1180