There are several sites that will tell you the theme and plugins used on a WordPress site. Ask the googles/bings/ducks for “what wordpress theme is that”. The results may often include paid themes that have been extensively customized, but may give you a starting point.
As for how to do it – that’s a big question that depends on your skills. And how much is also a big questions – it depends on how much technical/programming knowledge you have, and how extensive you want the site to be. There is no good answer for both of those questions; and those questions are not within the scope of this site (which is probably why you got the downvotes).
There are themes/plugins that have visual drag/drop designers, so you can create your version of a theme with all the elements you want. Examples are Divi, Elementor, and others. But even those tools still require a bit of effort and knowledge (and design sense), so can be complex to use.
Overall, your question is not really a ‘development’ issue, and not within the scope of this site. But perhaps my answer will point you in the right direction.