I'm not talking at high levels like gold league and above, though if this turns out to be true even at those levels that would be terribly interesting.

I'm simply wondering if it's at all possible to use the recommended item lists and still excel at the game if your mechanics aren't too terrible?

I ask this because while I'm an experienced player I am most certainly not an advanced one. I'm having a lot of difficulty with deciding what items to buy in a given situation and a lack of reliable guides that aren't incredibly specific to isn't helping me work all of this out. While I do want to eventually become a better player overall I'm just having trouble making smart item decisions.

I've seen some threads around here in the past were platinum level players mention the importance of items, what to buy, when to buy, when to upgrade, when not to upgrade, and so on. They just almost never expand upon this.

Incidentally, if you know of any good item-centric guides with concepts that can be broadly applied that would fantastic.

I'd say yes in most scenarios the list isn't to bad

just pay attention to a few things..if the enemy mid is 10-0 buying frozen heart probably isn't the most important thing you should be buying

i am sure i could build only recommended items every game and i wouldn't drop too much, i am gold 2 which is equivalent to 1700s, i don't think i would even drop a division

recommended items are actually okay now before it was much harder to get by with just recommended

Now it is since there's actually a lot of options and diversity, before, no.

Recommended items have improved a lot with the new shop that came with S3, because they encourage players to build dynamically. That is, building items to react to the game you are in, rather than building a set list of 6 items in a set order every game.

I highly suggest against using item build guides. If you do use a guide, only use it as a guideline. Focus on the parts of the guides that explain why you are doing what it says.
If you don't already know what every item does, read up on all the items. Make sure you know when an item is effective and when it isn't. If you're getting kited as a melee character, Shurelya's will always be more useful than a Bloodthirster. If you're super fed though, a Bloodthirster might be just what you need to push your advantage.

The recommended items in S3 are almost dead on for most champs. Back in S2 they were just... well Akali's said to build a Phage.

Each champion has at most 2 items they can always get and have it be a good idea - sometimes none. There will always be a lot of things you get often, but good players build reactively every game. The enemy comp, builds, lane positions, and gold distribution all affect what you build from game to game. It's all common sense, but you have to think.

Recommended items of the new shop are way better than what they were in the old shop. I probably get at least 2 of the 3 core items regardless of champion and generally one of the recommended offensive items as well. However, the rest of my build is likely to stray away depending on the situation.

Nauts recommended items are pretty good.