Hi,

Disclaimer: This is not a request for a concrete build. I don't have the money to build my pc yet, so I don't want to ask about a concrete build. I just want to learn how to choose components to suit my needs as close as possible.

Summer sales are coming near, so possibly some interesting sales might be up soon and I might be up for at least some cheap parts. However, I've only been using low end parts, which are completely insufficient for my present needs, so I want to get myself a bigger gun PC. I don't have a problem with choosing approximate specs. I want to use my pc for programming, video editing, video design and machine learning, so I have come up with these notes so far:
AMD Ryzen 7 1800X (I guess this is this only part that won't change)
16 GB of DDR4 memory (Necessary for machine learning, cannot go any lower than that)
3 TB HDD (1 TB is just not enough) with 7200 rpm
and possibly a 4 GB graphics card, because I don't need to game everything on ultra settings 240 fps.
However, I am a bit stuck here. Because apart from these there are also RAM speeds, latency and other stuff. And the price difference between the slowest (2100 MHz) and the fastest (3200 MHz) can be significant. Not to mention, not all motherboards can support all RAM speeds, so if I buy too fast RAM, I'm essentially wasting money.
Of course gpus have the same thing. They have clocking speeds between 1100 and 1300 MHz, but the prices between them are marginal. I'm not entirely sure I need the fastest graphics card though. But are the slowest ones sufficient for today's games? (the best example sitting in my library is currently f1 2016 and technomancer)

So, how can I orientate myself a big better in these smaller details like RAM clock speed, cache size,... etc.?