[noah-kun]

Batteries would be the easy part :). But with your level of knowledge, I'd suggest you first buy a used Macbook, maybe even a broken one, and find sources of hardware to replace/improve the machine affordably. Also do some Arduino/Rasperry Pi projects. (I've been a software dev for 5 years and I'm learning a lot doing the above myself.)

I believe there are a few open source laptop projects in various states of completeness and goodness. Some ARM, some PowerPC, and so on. There was also OLPC.

Here's some links. You'll notice you might not like the options. One is an ultraboook with 1-2 USBs. The others are like, high school science projects :P

https://hackaday.com/2017/02/05/olimex-announces-their-open-...

https://www.crowdsupply.com/sutajio-kosagi/novena

https://www.crowdsupply.com/eoma68/micro-desktop

I'm pretty sure there's some better ones, but ther you go. Oh, and to make your own board schematics and designs for 3D printed cases I suggest a Macbook Pro, 2012 or later.