Should I buy Cities: Skylines? The sim part sounds fantastic, but I also don't want to get sucked into DLC hell. Every time I look at the store page, I start scrolling through the DLC list and my interest just ... fizzles out. Every single DLC looks like it contributes something interesting, but the one bundle is like $155, and that's after a 9% discount. Ugh.
The good thing is that the game is totally playable even without DLCs.
The bulk of the game are mods more than anything, and every DLC brought with it a beefy free update containing the core changes, so by and large new mods should work no matter what.
Anyway, my approach with C:SL DLCs has been to just pick the ones I'm interested into.
For example, Snowfall and Mass Transit added a lot of transports options, and I love them.
Natural Disaster brought disasters (duh), and I've never really cared about them since the Sim City days, so I've never bought it.
All in all, pick the base game, try it for a while, start subscribing to some mods (IIRC the most downloaded/rated lists on Steam is good enough to start) and see how it feels.
It goes on sale all the time and on many stores, so you'll have time to pick the DLCs up.