The information economy requires the individual to manage lots of information in order to earn a living. Modern personal information management requires computer skills. Managing one's personal IT infrastructure requires info management capabilities.
Thus we have a chicken and egg problem. Where to start?
Well, the chicken evolved, and so can you.
The most powerful toolset is open-source software (OSS). However, it has a significant barrier to entry - expertise. Learning is the hidden cost of OSS.
Ultimately, Emacs is the tool that allows a non-technical user to bootstrap to control over his OSS IT environment. Within that, Org is the tool that allows him to bootstrap to control of Emacs. Thus one of my goals is to streamline adoption of Org by non-technical users.
Once he's familiar with Emacs and using Cyborganize, the user's ability to consume and manage text and binary data is limited only by the effort he's willing to invest. Until then, however, his info management systems will scale very poorly. Therefore it is important to simplify the bootstrapping process as much as possible.
Presumably one has learned pen and paper in school, so start with GTD's paper filing system. (Why not pencil? Because it must be legible years later.)
That will suffice to buy a computer, which should run MacOS on Apple hardware. Expand that to an Apple laptop, desktop and smart phone. Used is fine, as long as it can run the latest OS. Check the update schedule to determine when it will become obsolete. Don't upgrade an OS immediately; wait at least 6 months.
Buy the overpriced support contracts at first, but not the extended warranty. Instead, be careful with it. "Being careful" means Googling before doing things such as trying to clean the screen. Computers dislike heat, vibration, radiation, and dust. Buy the backup plan.
Start using the Apple ecosystem of apps, and/or Google's, according to taste.
The next step is to begin transitioning one's main PIM knowledge base from paper to digital. Evernote is a good bridge, since it emphasizes capture ubiquity and paper compatibility.
Don't invest heavily in populating non-plaintext PIM databases at this stage. That work will be lost with the transition to Emacs org-mode. Evernote is Org compatible, so it's an exception.
However, using a PIM such as OmniFocus for simple task and project management is fine. And obviously use whatever productivity software your workplace adopts.
Congratulations, you've reached the hipster edge of nerd. Now it's time to become totally uncool by learning Emacs. Prepare yourself by purchasing a Weird Al Yankovich album and building a shrine to Richard Stallman.