Okay so, there’s a LOT to know when getting into Warhammer, but once you have a general idea of what side of the franchise you want to get into, it’s fairly straightforward. I recommend looking up Cosmonaut Variety Hour’s guide on YouTube for how to get into it, it’s very concise and gives you a ton of tips on how to save money (this shit can get VERY expensive very fast)
My personal recommendation: look up armies that typically take a smaller amount of troops to have a “kill team” fit for smaller scale games and start there. Adeptus Custodes, Space Marines, Adeptus Sororitas and my personal fav, the Grey Knights, are all relatively cheap to get into and fairly easy to paint (yes, you put together and hand paint the models in the game yourself)
Honestly, there’s a lot of people who just buy models from a bunch of different armies at random because they’re ONLY into the painting side and not playing the game, and that’s totally valid! If you DO want to play the game tho, you need to have some forethought as to what units you’re buying because they’re not interchangeable and can serve specific roles in an army. I recommend looking up lore vids/ breakdowns for different species and armies to see what part of the world you find the coolest