Not really what you specifically requested, more like another opinion in general. Hiya, I'm bizcuit, bbq's resident babbler. :)
In no particular order.
Really no substitute for earning your chops imo, when it comes to gnu/nix. Just the way it is, more time, effort, experimentation = you learn stuff. Have seen people new to Linux rocket past much more experienced long time users, in a relatively short time span.
Though my working theory on this is a) They already were predisposed to tech. Intelligent, logical ... well reasoned people, who take to even complex subjects like fish 2 water. Just for me, that's one of the appeals of gnu/Linux + open source. The folks who design this stuff are very intelligent, logical and well reasoned people. Results and the scientific methodology oriented. Either hard, reproducible data + results ... or it didn't happen kinda thinkers. So the resulting products of their efforts are the same. I personally really like that.
b) Plus with the above, once they got a taste of gnu/Linux, got obsessed with it and therefor read/tried every fricken thing associated with it they could get their mitts on. In the process devoting A LOT of time to it.
Pretty straight forward equation ...
If someone not really passionate about something, spends 3hrs a week for 10yrs learning/using summin vs someone who is stoked about that subject spending 16hrs a dy for 3-4mnths. Not really surprising they blow right past the former in skill and knowledge related to it.
Another excellent way, that really helped me in learning things ( not that I'm any kind of nix ninja). Was actually helping other folks solve their problems. Over at Linux Mint forums, used LM10 for probably 1 1/2mnths but stayed a member of the community for quite some time afterwards. At that time, was a noob myself but was better than avg in terms of google-fu and wasn't afraid to dig around in LM10 or other OS.
Ended up helping many a Mintite and in the process learned a crapton myself.
Don't be afraid to dig in and break-stuff. Also when 1st coming over to da power of da source, was already a uncontrollable tweaker and software optimizer and much of the things learned on Window$ to a great extent directly translate(d) to gnu/Linux.
That being optimizing settings to reduce overhead, substituting lighter utils/apps to replace bloated ones, disabling unwanted background services or ( daemons) that I didn't use or want running or autostarting. But with LM10, everything is highly config'ed for you and customizing it w/o knowing what someone is doing, could have disastrous performance effects or unexpected quirks, that at the time I had no idea how to undo or what files to change to fix what I'd done.
And so I did the noob fix-4-everything. Reinstalled, lol ... time and again and started keeping a list of all the things I changed, uninstalled etc etc. So being too stubborn ( read kinda dumb) to find one of the gazillion ways someone can easily backup and restore a full Nix OS. Eventually learned which files to edit or things to dork with to control and fix stuff.
According to one cool #! user, I haven't seen or heard from in awhile. "No matter what you want or are trying to do, it's all in a file somewhere." 2manydogs.
I'd be stuck spending hours, repeating the tweakage process, over n over, n fricken over. Until I'd pick up where I left off, screw something new up and then yep, start over yet again.
c) It's not whatcha know, it's who you cyber stalk. :P Some nixers you come across, you can just tell know their fricken stuff. One such obvious case is Machine ( and others here, some you mentioned.) Nothing wrong with back tracking through their forum post/history. Someone could potentially learn a lot by reading those posts and googling related stuff that seems useful/interesting.
Just like anything, find resources online. No shortage of sites/forums etc related to cli gnu/Linux, scripts ... whatever. Often found when it comes to Nix, someone somewhere had long since discussed it or done. Longggggg before I'd even known there was such a thing as open source. Join some of those forums, browse all the info they've provided and get your hands dirty 1st hand trying stuff out.
Love Debian, you're not alone in that. Do some googling about stuff like "minimal Debian netinstall" and variations of same. Plenty of how to's on the topic. This brings me to yet another babble pt, think it really helps to use/choose the right distro. With most the mainstream biggie distro's. So much is preconfig'ed for users and layers after layer added in the way the distro maintainers want things to be. Whereas others, (ie: Some of the bbq's) strip that stuff away and let you get to the underlining stuff or "under the hood". Still really like and support LM but if you really wanna buddy up with Nix, not the best choice imo.
Finally (gawd da babble is giving me a headache too !) Wouldn't be surprised if someone here has already told you "live in the command-line". Wouldn't say do that, without 1st spending some time learning about the subject, though if that's someone's end goal, would say make more effort to spend more time there.
Sighs, ok done ... listens for da sighs of relief. :P When I grow up I still wanna be like the Baconator. Vll!