Best way to buy Minecraft for PC?

[pumaz]

I want to buy minecraft for my niece to use on her Windows 10 laptop, I know nothing about the game and believe there's several ways to buy it. Where and what version (most popular) should I buy?

 

[pumaz]

I saw they had an offer on the Windows store for about £7 but wasn't sure it was the best version, so basically the minecraft store version for £17 odd is best?

It's for my young niece, believe me I have no interest in Minecraft lol