Couple of things I could suggest:
1) lose the sandbags kit... scratching out your own tend to look more realistic. Guys on here use a variety of sculpting compounds. The plastic Tamiya kits and the like don't usually look too hot.
How about a simple road or field setting? Nothing too specific. Just get your skills flowing. What you could do is determine where the crew might be when choosing the decal selection. When you know "who" the tank belonged to, google that regiment or division to find out where they saw action. For your first dio, I'd strongly suggest a drier climate... Custom Dioramics and 135 Construction Battalion sell good resin street sections of brick and cobblestone, if you wanna get urban. It can be cheaper and more fun to make your own brick street as well. Those manufactures, along with Verlinden, also offer decent building and house starter kits. These are fairly easy to assemble, not incredibly expensive, and according to the style building you may choose, can help to identify the location for you. Although water and snow dios are better when you apply those materials to basic terrain skills that you've aquired, go with whatever gets you inspired. It doesn't have to be perfect. It's more important that you have fun with it. If you want to see how I make a simple road, look here. My methods are not original, but they are easy.
When you decide where these guys will be (Normandy, Holland, Italy, etc), browse through your reference library and google images. You're brain will take over. Again, it doesn't have to be too specific to location or battle. Take progress pics and post 'em, if you want guidence along the way.
Hope this helps a little,
Steve