Bouargh

Stuff from GSC range and Incrusor bits can be good sources too:
- Light marker (Machine gun accesories) or spotlight (especially the shoulder mounted bulb):
 

 
- Scanner:
 

There is strictly no advantage I can see into using the Despoiler as a melee knight.
 
Rampager have more attacks and impact for melee in all aspects. With these extra attacks + Sustained hit on Rampager in charge you are IMHO more than compensating the rerolls of the Despoiler. 

Almost any pistol from the Adeptus Mechanicus range would fit.
Especially from mounted Skitarii (Serberys) pistols or a Tech Priest Dominus pistol.
 

Hi,
 
It is indeed quite an expensive army to collect. And even worse since the last dataslate. Anyway, in general, you reach AdMech more for the outlook rather than for the economy.
 
As far as I am concerned, I started with a Patrol and the ooP Reinforcment box (Duneraider, 1 squad of skitarii and an engineseer). Then some various stuff from FW (Termite, Mago and Abeyant). I recently added a Maniple too.
 
Yet I would rather advise, if you already have some knights, starting with 2 Combat Patrol. It is a solid core. But you would need some characters. The Manipulus is for me a must. The Technoarcheologist is nice too, but you could kit bash one of the 2 Engineseer you get, instead of buying one. 
The Extermonation maniple is nice but may be as a later step. It remains however an interesting deal so, if you can seize one, better now than never. Yet, it might lose some interest in the next months as, if some repackaged deals come out with the codex this winter, you might end up in a dead-end alley for future boxes: One advantage of the box is getting Cawl inside. If future deals are built up aound him, they will loose their saving advantages a lot.
 
Now, as the Maniple comes with 2 units of Kataphrons, if you want to field some quickly, it is a better way than the second Patrol box... Indeed these Servitors are often unavailable. And according to the current meta (or at least the coments around it) it looks liek Kataphrons are the rising stars of the army. I have no opinion on respect of this.
 
So as a summary:
1. My first advise would be 2 Patrol boxes
2. If the Deal is more attractive money wise, swap the second Patrol for a maniple
3. In any case, get extra characters (Manipulus for sure)

I would not over interprete what looks like being a failure of the system. Indeed, would they have wished acting in a direction of "normalizing" stuff while getting rid of a keyword, they would have cleaned first the names of the minis. I feel like the search engine is looking through names and eventualy some metadata. But these metadata are not the filters themselves... But in most cases through names only and nothing more.
 
For example, typing the "Fly" keyword in the search bar, will sort out the various flying stems and... Farsight - 6 products visibles. And even there it works very bad as clicking the "view all" button makes appear only Farsight - you loose all flying stem. And the Commander does not even get any "Fly" word in its name or its product description (CTRL+F search). Only a keyword in the filters. 
Now, if you type the "Imperium" keyword, you get 13 entries, out of which 6 entries with Imperium written in their name, and 7 without. While the keyword is supposed to be associated with 329 products listed in the filters...
 
I would not consider any malice in the failure of searching with "Primaris". But just a consequence of an ill/poorly done webdesign of the search engine. 

Hi,
 
As far as the official tournament scene is concerned, the lately published guide (hlF8WKv4gJpXPZha.pdf (warhammer-community.com)) tat is based on the ITC system (more or less) can be an useful reference.
 
Terrain heavy.
 
Otherwise it is all a matter of preference: I personally like city fight, so lots of ruins and vantage points, LoS breaking obstacle BUT some roads and alley that are more or less as width as a LandRaider in order to structure some quadrant.
There is no rule really, it is more related to the fact the you want to standardize with casual pick and drop games or if you wish to go to a more narrative format.
The current ITC stuff reminds me rather of Jungle fight table, quite dense, when Codex Catachan was issued - but it is fine for a standardized apporach
Anyway, if you go at scenarios, you do what you want: a flat table with little obsatcles and 2 o 3 hills and a few rumbles can be perfet for a tank battle on a plain, whereas your shared pics is gorgeous for almost any kind of encounter in suburbs...