Does our wargame of all things now need a disclaimer when help is asked for? I'm far from British, and I don't pay hundreds of dollars for a game in which I get my ass stomped by people that just tell me to "take what I like, it'll work out". Tried that. Got my ass kicked.
List tailoring is the wrong thing to do, you'll just lose when you fight someone with a different army concept. However, balanced lists, like the aforementioned Tau, do well enough across the board to be quite viable.
Playing what you like is a shot in the dark for it being any good. My Khorne-themed CSM list:
Kharn
2x 8 Zerks, Pfist Champ, EA Rhino
7 Zerks, Pfist Champ, EA Rhino
3x Dreads, MM and EA
2x8 Lesser Daemons
3x Obliterators
Possessed Vindicator
Defiler
If I don't get first turn against that Tau list, I'm praying for cover. If I do get first turn, maybe the Defiler will do something, and the Oblits might harm a Hammerhead, the rest of the army is moving forward. They hit a Piranha wall on the Tau turn. The Railguns then make short work of the Defiler and Vindicator, while the suits fire at the transports. Probably markerlight the one Kharn is in, take its cover away, and force him to march. Bottom line is that the Tau are far back enough on the edge to keep my army away by way of blocking and Kroot walls, and this buys them successive turns to fire away with impunity until the enemy lies defeated.