Gonna throw a disclaimer, I hold no business and financial interest in the below, gonna just dump because I think IMO worth taking a look
The overlord's blog is pretty solid place to start, he also has a cookbook. (Working scripts)
https://stoic.software/
Overlord Matt Dahse's book
https://leanpub.com/netsuitedevelopment
Good blog that I follow too, quite good quite good.
https://netsuite.smash-ict.com/
Learn to use this.
https://www.netsuite.com/help/helpcenter/en_US/srbrowser/Browser2020_2/script/record/account.html
Chrome is your friend.
There are chrome extensions essential for NS, you can take a look, especially for dev. Just faster!
I think IDE is a giant discussion, I use atom and I can point you in directions but I believe everyone else uses anything with SDF (Suitecloud Development Framework i.e kinda like the Git NS?), say Eclipse or Webstorm
Rather than Javascript, I think Node is closer for SS2.0, so more like npm stuff, it's more advanced (in terms of your SS journey) but once you are more familiar you'll be able to use those libraries in your SS as a bonus.