yoink I think I'd hold off on The Ordinary until you get to grips with what exactly it's about. I think it's great they're bringing these type of ingredients onto the market at democratic prices but as I was discussing upthread with Nabootique it really isn't a beginner's skincare line and you really need to have a good understanding of your own skin before jumping in on those. I'm finding it hard to recommend a beginner's guide as most will follow a certain philosophy towards skincare/are outdated.The Caroline Hirons cheat sheets are often recommended and while I do agree they give a decent intro it is very specific to her philosophy and she tends to change her tune on certain things so some are outdated and the site is difficult to navigate.
What exactly are you finding difficult, the routine, products, where to start, etc. ? I don't know if it's worth starting a separate thread over but ask and I'll try to answer.
I'm trying to search the 'threads I'm on' thing as I've answered some other posters at length that could be useful but I'm having difficulty locating the one I was looking for, I may have a backup version of it somewhere.
Pupsiecola there are several things that while non-comedogenic can be clogging, irritating, etc. There's derivatives of palm/coconut, mineral oil, sulfates, etc. in the lotion so it would be hard to tell what. The other has retinol but no indication of strength along with a patented ingredient containing a form of Vit C. All potentially irritating, there's endless possibilities unfortunately.
The pH matters mostly in cleansers and acids (oils have no pH). Our skin is slightly acidic, when it becomes basic/alkaline it is more prone to acne, rosacea, etc. etc. A lot of cleansers (especially the foaming SLS types) are high pH (ie. alkaline) and disrupt our natural acid mantle making it susceptible to bacteria leading to issues mentioned above where acidic cleansers don't disrupt. For more info on cleansers this post is worth reading. In acids it matters because in order to be exfoliating there is an ideal pH. Too low and it damages skin (think lemon juice, neat apple cider vinegar), too high and the active ingredient won't work as effectively as the concentration needed would be insanely high due to the difficult maths I mentioned upthread, this post explains it better than I can.