You've come to the right place for Kubricks! Here are a couple of suggestions and notes for you:
#1 - Ebay is great source for Kubes, but you need to be patient. There are some sellers like Honorus that have a big supply, but only offer 1 of each figure at a time at ridiculously high prices. Wait to make sure you're getting a good deal or this hobby can get spendy fast!
#2 - JediDefender classifieds or Kubricknation.com forums are probably your best bet to get figures outside of Ebay. You can find some of the more common figures on here for just $5-10. The front page of Jedidefender also has a photo gallery and checklist covering the first dozen waves or so. The Kubrick threads here have pictures of everything since then as well.
#3 - If needed, you can turn to some Japanese suppliers. Celga and Onejp are middle-men that will allow you to bid on Yahoo Japan auctions. You can get some good prices on rarer stuff this way, but it is not a great route for common items as you have to pay shipping fees twice, give them a commission fee, and put money in your account ahead of time to bid.
In general, you should pay attention to the case ratios. Lower ratios mean the figure is more rare and will probably cost you more. Each release has included boxes of 12 figures. In the older series (pre-deluxe), there were 6 basic figures, 1 common chase, and 2 rare chases. In the deluxe series, the common chase has been removed in place of the Build-A-Figure/Ship.
You should be able to get most of the basic series figures for $5-10 unless they were short packed. Series 3 boxes, for example, only had one AT-AT Driver, so he will cost you more. The "common chase" figures were 1:24 or 2 per case of 4 boxes. Those tend to go for around $20-25 I think, but you can sometimes find them really cheap. The rare chase figures are 1:96. Each case of 4 boxes only includes 1 rare chase figure (so 1 in every 48 figures). You would need to get at least two cases (8 boxes) to land both chases - possibly more, since you can't tell which chase you get from the outside of the case. Those chases typically go for around $100. Deluxe Chases may go for considerably more. We've seen Hammerheads go for $300 and AT-ST Drivers go for as much as $600, which is insane.
Your best bet is to go to the advanced search in Ebay and looking at completed auctions. This will give you a good sense of what the figure(s) are going for. You can always just pse your questions here as well - JD'ers love to talk about Kubes. Good luck and welcome to the site!