Editing Warhammer 40,000/8th Edition Tactics/Adeptus Mechanicus (section)

=== Buying ===
So you want to start hoarding technology and shooting cancer at people, but where should you start? The Skitarii Start Collecting box is excellent value, getting you a unit of Vanguard/Rangers, your first Onager Dunecrawler, and your Techpriest Dominus. All units are pretty much mandatory when running a strong Adeptus Mechanicus army. The Start Collecting box comes at a decent discount over buying the units separately. Notably, buying a seperate Dunecrawler is almost as expensive as buying the Start Collecting box, so when you feel like you need a second Dunecrawler, just buy another Start Collecting box.

Two Start Collecting boxes will net you 20 vanguard/rangers, 2 Techpriest Dominus, and 2 Dunecrawlers, which is an excellent starting point for your army, as it will be the backbone of whatever else you decide to field. Remember you can field your Vanguard/Rangers in squads of 5, so if need be, you can run four 5 man squads. A solid purchase after you have the basics down would be either Kastelan Robots, or a few close combat specialists like Sicarian Infiltrators, or Electropriests (though they are by far the ugliest models GW has ever produced.
*You can now get the Fist of the Omnissiah box (No longer in production) for that second Dunecrawler that you need, an Engineseer, Kataphrons, and another set of Vanguard for $170.

Alternately, Forgebane comes with a Techpriest Dominus, 10 Vanguard/Rangers, and a pair of Knight Armiger Warglaives. If you can find a Necron player to split it with (or have/want a necron army), it'll make for a good supplement as well. 
*No longer in production, you might however find one in a non-GW hobby shop.

There is a new Start Collecting Box and it is pretty awesome. You have your standard unit of 10 Ranger/Vanguards and a Enginseer, not the coolest thing ever. But then you get a Skorpius. A few of these and you have your infantry of choice and either their rides or the best Mechanicus tank lined up and ready to go.