I would just buy a bulk lot of commons. Maybe 40 figs for $40 (with action bar and character cards) and not too many duplicates. I'm sure you could find a deal like that on eBay or somewhere. Don't worry about rares and epics right now. You might want UBases, but it's cheaper and easier to just use dice to keep track of hit points (d6's) and ticks (d10's).
You'll want to get a few maps. As your local shop that carries minis is they have any. 2-3 double-sided maps will keep you going for several months. It's best to play on a map several times, so you can revise your strategy as you get more experience. You can find some on eBay if you must buy them.
When you play, randomly hand out 10 figs to each player. Then each person should build a 3-man party, ignoring faction restrictions. If there are 2-3 of you playing, you could divvy up the figs by faction and play faction-only parties.
Let us know how it goes!
PS: I just found a collection on Ebay with some epics, rares, dice, customizable maps and some promos for cheap ($55-- ends in 20 hours, so hurry!). Go there and search for: Warcraft Minis Collection