But they are also the least common ones

.
Weirdly, graphene is super common and renders most chemical farming null by simply stacking them up (though needing these for suit upgrades will deplete the stock quickly). But chemicals don't tend to be the bottleneck, in my experience. I find the bottleneck is usually tech, then circuits. So weapon components are gold dust and I usually end up just needing to trade to fill the expensive orders required for these.
Back in the day, microelectrodes and fibre were super common if you relogged at POIs. I don't know if you can still do that these days (I'm guessing not).
The advice here is generally good but it does expose the flaw in the game's upgrade system... EDO's material gathering meta is basically "grind lists of everything you need by gathering everything within the bracket you want then trade across" and it's not awe-inspiring game play, if I'm honest. The dopamine hit you get from trading 600 trash items to get the 30-40 rarer items you need is actually close to being inverse when compared to other games that reward you things you actually need by doing things you actually want to do.
In terms of game reward design, Elite does this a lot and seems to take the approach of declining hits (that is, you're investing time into getting things you've got no specific interest in and are then expected to "destroy" them in exchange for smaller quantities of things you do want in a system that barely registers on the "good feels" hit scale when you actually take part in it... i.e., manipulating a menu system and not actually playing the game).
Imagine a system that ordered things the other way around, giving you tasks to complete that resulted in a big hit of the items you actually want. The mission system almost does this, except it's limited to 5 (or more but only if you get very, very lucky with RNG) and doesn't include tech, chemicals or circuits. Even if it did, at a max of 5 per, you're still going to spend way, way more time grinding the lists out via missions than if you did it via bucket trading. It could be so much better. Like, you need 15 microelectrodes, right? Speak to an NPC at a suitable settlement (base "suitable" on the concept that it's the right type to have a supply of circuitry) and they provide you a list of items they can supply in return for a mission. You do the mission successfully and they'll then give you a way point elsewhere that you can go to, be it a settlement or POI, and there you'll find 15-20 microelectrodes spawned for you to collect. As you gain faction standing, the list of items they can offer increases and the end value of the reward increases. Microelectrodes may not even be on their list initially.
This adds a progression system that gives frequent dopamine hits whilst building reputation with various NPCs who offer you more options for performing missions to then unlock the locations for greater volumes of materials. All this takes time. It's all just "doing the game" but it ends with you being able to source items you need at an accelerated pace, albeit needing to still move about the galaxy quite a bit to achieve full lists (and, as Elite's factions are in a constant state of flux, you'll need to build up reputation with several different NPCs anyway).
It's just one idea. I could think of more. Elite just shows no interest in applying this sort of game play to its material gathering systems, which are all largely based on RNG and heavily reliant on the very dull trading system to work. If you want a thing, you generally cannot just go get a thing. You can go to a location with a chance of getting that thing but you need to do that same RNG dice roll 5-25 times depending on the thing. It'd be so much more fun if you could just "do things in a list required to eventually get a thing".
Edit: Just an aside, I saw a comment or two above (and these are typical in these threads) where someone is saying "just stack them up, I have 600 of them now because I just traded across" and so on. This is said from the position of someone who hasn't
needed these items for a long period of play time. It's not very useful for the person who is asking the question (basically, you're saying "just play the game for months and don't upgrade for a while and you'll have everything you need to upgrade.") I see this in EDH discussions as well (just do missions for G5 mats and trade across; I have 100 of everything now!). Yup, we know you can max out storage of items "over a period of time" doing stuff and engaging in the dull trade system; saying this from the position of someone who has fully engineered ships already is misleading. This is not useful for a new player who is just starting out. The same is true for EDO. Using the trade system is essential, so it's good that the OP got told that information (as dull as a system as I think it is, it is essential) but letting them know that you've "easily" gathered 600 microelectrodes is misleading. It's not easy. It takes ages to do (not to mention requires a ton of inventory management to achieve, let's not forget that) and demonstrates only that you no longer require those items. The player who needs the items doesn't have that luxury by default and this advice is only useful if they're already done with the engineering loop and are just playing the game (useful because they may one day want to try another suit or weapon out).