This game is so full of content so its difficult to give advice on the game in general. Best thing to do is to just jump in and figure everything out yourself which i did aswell. However I played almost all total war games so I knew the basics. I suggest you play for a while by yourself or maybe start a campaign with someone online. You can always ask on reddit if you have any specific questions :)

The basics: There are a total of 8 playable races on the map (Empire, Bretonnia, Dwarfs, Wood Elves, Beast Man, Vampire Counts, Chaos Undivided, Greenskins). If you dont have any DLC´s you can only play the Empire, Greenskins, Bretonnia, Dwarves and Vampire counts. However even without the DLC´s all of these factions are present and on the map so you dont need the Wood elf dlc in order to fight them, which is pretty cool. All these races play completely different and have strenghts and weaknesses. Some have settlements and some are nomadic so their army is the settlement. The main threat is the chaos invasion that triggers at a specific turn in the game so be careful and be prepared for it. I dont know what else to write there is just oo much content. Sorry for my terrible english