I have both the Core Set and Revised Core Set, plus the Command Squads and Spec Ops (Observers + Snipers) for both Allied and Axis.  I'm thinking about getting the Light Walker for each faction and 2 more of the Mediums since the OCS walkers do not have all weapon configurations available. 

The question is: do I need heavy walkers soon, or can they wait until I get these and the rest of the foot troops?  Can/should I sacrifice a medium (for each faction) to get the heavy sooner?

My local meta?  I'm it.  2 stores within 45 minutes that sell DT, but no one plays it.  Trying to get my friends into the game and want a well-rounded start for both DT and DW.  So I really need 2 armies that look and play well.

In my opinion the heavies can wait. I'd put the heavies at the very end of anybody's army list. They're cool and all, but their cost/benefit is pretty doubtful, and there can only be fielded properly in a small selection of missions.

I agree with Loophole as far as DT is concerned, but for Dust Warfare, Heavy Walkers are almost always a good choice in your army.  So if you're really itching to get them, go for it.

For the medium walkers, don't forget the new medium walker sets, the Wotan/Flam-Luther and the Cobra/Rattler.  I say if you're going to get 2 medium walkers per side, get one of the older kinds, and one of the newer ones, for each faction.

I am in a situation comparable to yours, frogimus, and I decided to invest in squads rather than in the heavy walkers to have more options while building armies. The heavys are rather expensive and consume a lot of points in your army as well, thus limiting your other options.

 Thanks for the advice, folks.  As cool as the heavies look, I wasn't sure they'd be an immediate impact - especially since I and my friends will be learning the game.

Well, that leaves 5 troop packs for each of the original 2 factions and Op Seelowe to get the final 2 heroes Forgot to mention that I have Cerberus and Cyclone).  I think I will finish out the foot troops before any mech purchases.

55 painted, 25 on paint table, and 34 more to get.  Awesome!

I think you've made a good choice.  In Dust Warfare, you're limited in how many walkers you can put on the table, so investing in more squads will definitely give you more options.

 A SturmKonig is an awesome asset for an Axis Army. It can kill well in all three categories. Sure it is expensive, but it really pays off.