What desktop computer should I get?

I apologize in advance for my lack of knowledge pertaining to computers, I know very little when it comes to processors and performance. I want to get a desktop computer for a few reasons. 1. Better storage compared to my laptop. 2. Better performance. And 3. To replace a T.V. (sort of)

Better storage is pretty self explanatory but as far as performance I need it to handle things like ArcMap which uses shapefiles. The projects here get fairly large and really bog down my laptop. Also, I have a GoPro that can record in 4K video quality which my laptop also can't handle. I will view and edit these videos so it needs to be able to handle things like that really smoothly. I would also do some gaming but not a whole lot, basically just Minecraft and games like that which run slow and jumpy on my laptop. Finally I'm replacing a T.V. Which I rarely used so I want something with a decently sized monitor so I can pop in a DVD or watch netflix on it but still be able to clearly see what I'm watching from 20ft away.

I have seen things like the All-in-one computers which look like they have pretty good sized monitors but outside of that I don't know how powerful they are.

Any suggestions would be greatly appreciated so I don't have to go into a store and have them tell me I have to get the most expensive computer with all the fancy ad-ons when the cheap one will work just fine. I will have a price limit of about $800.

You won't get a good enough computer for all that for $800 you are looking at a 4 or 8 Tb hard drive to start with and an i7 processor with 32 Gb ram

You need to expand yer budget. $800 is too low to handle 4K