Dominons 5 is a 4x game with amazing complexity and pretty awful graphics.
If you are new or casual to 4x then play Endless Legend instead which also has deep complexity but is more friendly with its excellent UI, wonderful look and story and easy to learn hard to master complexity. Civ VI is another good choice but more expensive than Endless Legend which released in 2014. Endless Space 2 is a space version of Endless Legend and another great option.
If you're kind of played out on those other games and want something new to get your head round then holy moly is Dominions 5 the perfect answer. It's so big that I've restricted myself to just exploring and figuring out the Ancient era, treating the Middle ages and Late Middle ages parts of the games basically as unopened expansions I'm saving for a later date. Even doing this there are still 31 Early Era civilisations to figure out, they all play very differently, and they're each very complex to figure out. I love it!
Here's DasTactic's excellent Primer, so if you're interested in this game take a look. He also has a series of beginner's guides that will help you if you get it as the game does throw you in at the deep end.
If you find yourself enjoying it then I'd recommend the following resources:
Dom5 Mod Inspector. I always have this open when playing this game and alt tab to it all the time. Much of the information you will need to make your decisions is not available in game or is in an awkward format.
Dominions 4 wiki. Use with caution as this is for the wrong game! It's 95% correct for Dominions 5 though and certainly better than nothing.
Especially useful for newbies.
Deep high level insightful analysis. Also features excellent homemade skits and fan contributions making it quite deep in roleplay and immersion.
Waervyn's World tips for new players
Less accessible than the others but has enormous knowledge and does subject videos explaining a game mechanic not found elsewhere.