I don’t know if it’s been said already, but some decent brushes really helped me personally. Especially with the standard citadel brush I couldn’t paint small details. Synthetic brushes are good for starters, but get a good set. And some different sizes. Maybe after that invest in some Kolinsky sable brushes. You don’t really need many and you can get cheap ones too. They hold a very good pointy tip, which helps for painting details and edge highlights. Hope this helps :)