As a student and then a self-employed person, I went through several phases of experimenting with programs and devices to do my work. These have been the ones that have stayed with me.
Some notes app
I use Apple Notes for on-the-go notes and once in a while move everything over to Microsoft’s more structured OneNote for long-term storage.
Usually my self-control is pretty good. When I’m reopening Twitter for the fourth time in an hour and quickly running into the same tweets I just saw, I know I need the intervention of an external force. Three clicks of the Freedom icon on my Mac and I can block Twitter (and any other distracting site, if I need to) for as long as necessary.
If the Internet is something you use, this is important. I use Chrome but I have Firefox on all my devices as well.
Ever since I learned to use Unix in college, setting up a terminal (or the Windows subsystem for Linux on Windows 10) is always one of the first things I do. My .bashrc has been incrementally expanded and contracted and relocated for a few years now, allowing complete and portable customization of my shell environment.
(*–pedantic: Yes, it’s technically a “terminal emulator“. No, this particular language difference does not matter to me.)
A text editor
For code, short messages, drafts, and occasional distraction-free writing, I always have a text editor. The default programs are fine, but I like Atom on my Mac and Microsoft Visual Studio on my Windows desktop. If I’m running a terminal I use vim.*
*If you’re torn in a Unix environment, just use the one you learned first – vi, vim, emacs, nano, whatever. In almost all cases, the differences are less important than loud people say online.
An office suite
In 99% of cases this is Google Drive. I use it for word processing and for my sprawling budget spreadsheets. Collaboration is easy, the interface is pleasant, and it’s free. Microsoft Office has more features, though, so if I need more tools than Drive supports I turn to Office. Exception: I use Keynote on my Mac for presentations because I like it quite a lot. I seldom use any other presentation tool.
A scanning app
I don’t like to carry around a lot of paper. I digitize my receipts and other paperwork whenever I can. When I had a desk I could use a document scanner, but now I just use Scanbot Pro. Once I have PDF’s and upload them to the cloud, I discard the paper copies. I will almost never need them later anyway, and a few megabytes on a computer is better than several drawers in a file cabinet.
I do keep paper copies of tax documents and papers that are significant as paper artifacts, but everything else gets scanned.
Some bibliographical tool
This I used more as a student (and now faculty member) and I hesitate to include it in a list I’d prefer to be general, but it saves a lot of time. Most people can use Zotero. I work in CS where most people write in LaTeX, so I use the BibTeX format instead whenever I can. Usually citation contents can be directly exported in that format from the site where the source was accessed, but if not the LaTeX world is well-documented and most labels (e.g. “author”) are intuitive.
What I don’t use
I’m not a strictly minimalist person, but a lot of the utilities and helpful programs you can find online aren’t necessary. Investigation, installation, configuration, and maintenance take time that could be better used elsewhere, in return for questionable time savings in the long run. I don’t use a window manager on my Mac, for example, because mostly managing windows on my Mac is fine with the built-in tools.
Being cautious about what I install helps save time and delay the inevitable buildup of system cruft that has to be purged once in a while.
This is it
There are a dozen other tools I’ve used: QuickBooks accounting software, map/direction tools, chat clients, maybe an email client, etc. In specific cases, those are worth exploring and probably worth running. This is a list of what I consider a solid foundation for productive work for most people.