WARNING: PARADOX GAMES HAVE TONS OF SCAM DLC. YOU DO NOT NEED ALL OR MOST OF THEM TO ENJOY THE GAME. To make it easier for you, here are some DLCs I think you SHOULD buy and DLCs I personally enjoy that you shouldn't necessarily buy if you don't want. I advise you to BUY ALL DLC ON SALE.

You SHOULD buy: Utopia, Federations, Synthetic Dawn, Leviathans, and The Machine Age.
I personally enjoy: MegaCorps, Humanoids Pack, Necroids Pack.

That aside, the game is complicated but unlike some other Paradox games can be picked up quickly and the game has many mechanics to forgive the player for not understanding or engaging with other mechanics. Following the advice above, I think you will find it fulfills all your Sci-Fi Space Empire fantasies. As a great space man once said, "this is where the fun begins."