Hello!
Not ridiculous at all - in my first application cycle, I wasn’t able to pass ACs and interviews as I just couldn’t hack building my commercial awareness, so I totally understand what you mean! After a lot of trial and error, I was able to work on this skill and achieve runner-up of BIUCAC last year, so I can share what helped me!
I think your plan of starting with the basics is the best approach - this is the main thing that I focused on, and it is nearly impossible to analyse commercial deals without understanding the basics first. I found it helpful to use Investopedia and the Finimize glossary to review terms I wasn’t confident in. Whenever I came across an unfamiliar word, I’d note it down and revisit it later to make sure it stuck. Focus on understanding core concepts such as bonds, equity, securitisation, and derivatives - and keep an eye on topical versions of these (for example, green bonds came up in BIUCAC!).
Once you’re comfortable with the terminology, I’d recommend picking one or two reliable sources and following them consistently - for example, the FT, BBC Business, LittleLaw, or TCLA’s commercial awareness insights. Instead of trying to read everything, focus on a few key sectors that interest you or relate to firms that you are interested in. Over time, you’ll start to notice patterns and recurring themes, which makes it a lot easier to understand the bigger picture. I found it helped to work this into my routine - for example, I listened to the FT News Briefing every morning on my commute which gave me a brief overview of the most important business news each day.
As for following a story from start to finish, you could set up a Google alert or save articles on the topic so you can see how it develops over time. This is something that you will (inevitably) have to develop over time, so pick a few deals / topics that interest you and start following them now in preparation for interviews later down the line.
When reading a commercial news story, I always found it helpful to think about where a law firm might be instructed and which practice areas would be involved. This dual perspective shows that you understand both the legal and commercial dimensions. For example, in one of my VS interviews, I discussed the new Universal park being built in the UK, and highlighted how various departments across a firm would be instructed (e.g. employment, construction, finance, tax, real estate, etc.). It also shows that you can explain how law firms bring value to their clients!
You are definitely not expected to know everything! In my opinion, if you know the basic terminology, the most important things currently happening in the market, and how to look at a commercial deal with a legal viewpoint, you will be absolutely fine! It’s perfectly normal to tell an interviewer if you are not too sure on the topic, but make sure to give it a go and show them your thought process - this is often the most important part.
Try not to worry too much about being “fluent” straight away - commercial awareness builds gradually as you stay curious and consistent. Even trainees and associates are always learning!
I hope that helps and if you have any other specific questions, let me know! Remember, it’s a marathon, not a sprint - if I can do it, so can you! 
