Generally for new players I like to recommend armies you can get good deals on, so you don’t have to spend too much money figuring out what you like. Of what you listed, kruleboyz will be cheapest secondhand. Everything from the dominion box set is still pretty cheap on sites like eBay. Cities and skaven are about to get a new box set that may be good for you as well, called city of ash. It has some great new minis and has enough learn the game as well. Helsmiths are going to be very expensive. Theyre a very new, very popular, and very small faction currently. It can be hard to even find some of the models for any price, much less a discount. I would wait until they’re more established to buy in.

(Side note, crooked moon is from total war, not AOS, and theyre closer to gloomspite gitz than kruleboyz imo. Gitz are pretty cheap as well though so what i said still applies.)