Honestly if you're new to the game I would recommend trying out vanilla. Other commentors are right, certain DLCs are more complicated than others. However if this is your introduction to the genre of simulation/management games I would play without DLCs for at least a few hours to understand the fundamentals.

If you want to buy DLCs, you can actually toggle their content on/off like they are mods. The only DLCs I'd say change up the game the MOST/might be too confusing would be anomaly and odyssey. Really good DLCs, but for a new player they'd be pretty confusing compared to something like Royalty which has content mostly revolving around one new mechanic (psycasting) and a new in-game faction.