If anyone is interested in rts, I always grab one of the total wars with all dlc during the seasonal sales. Way cheaper to sleep on em and wait til they heavily discount the game + dlc.
Definitely can vouch for TW: Warhammer. I know basically nothing about the WH universe, but the playable races all have very unique playstyles. You could skip some of the DLC, though; all factions are in the game regardless of whether you own the DLC or not. Wood Elves are the only DLC faction I played as somewhat regularly.
I've been staring at Steam for the past two days and I'm still not sure what to pick up. So far I have the most recent DLCs for Democracy 3 and The Crimson Court DLC for Darkest Dungeon, which isn't even on sale, in my cart.