What computer to get to record minecraft gameplay?

How about Winders 7.

Wrong. Minecraft is horribly overdone on YouTube. Everyone has already found the Minecraft YouTubers they like. Those famous YouTubers will always be famous, and it's incredibly hard to break into that market. The famous YouTubers are the people everyone finds, that's why people find it so hard to create a gaming channel about Minecraft.

There's just no point in doing Minecraft anymore, unless you are incredibly funny or have some amazing skill at creating videos that makes your videos unique. Considering the pure amount of people that create Minecraft videos, there's pretty much no uniqueness left. Minecraft is over and done with when it comes to new channels.

You have to start making videos early in a game's life, the large majority of famous Minecraft YouTubers were creating videos in alpha or early beta (1.3 or around there). There are other games, for instance Starmade or Starbound, that are both newer, and you're more likely to get an audience with them.

I don't like being this blunt, I've just got so many friends that have tried to start a Minecraft channel and failed miserably, simply because everyone has found the YouTubers they like, and any potential new audience that searches "Minecraft" in YouTube always comes up with the same famous ones.

As for a decent gaming computer, look for at least an Intel i5, 8GB RAM and a 2GB dedicated graphics card (personally I favour Nvidia for a graphics card, but that's mostly a personal preference). Ideally you'd build your own one, but that can be very difficult for someone's first time, you'd usually get someone's help with it.