…I’ll bite. There’s a number of issues here…
First, the games aren’t even out yet and Yuzu is still in early development. Odds are it’ll get plenty of updates between now and the Pokemon games’ launch dates, so asking this now won’t really get you many good answers.
Second, literally everything you mentioned needs to be upgraded. Core 2 Duo and 1GB RAM? In 2019? I’m shocked you could run Windows 8.1 on those specs. If you’re serious about this (which I highly doubt but eh, I’m bored), you’d be better off buying a brand-new PC, it’d likely be cheaper than upgrading these parts individually.
Third, the price depends on your location. Assuming you’re in the US, it depends on where you get the parts from (retail or online), and prices fluctuate wildly.
Just hold off on doing anything until the games are actually released and see how they run in the actual emulator for the community. By that point, Yuzu will likely be further optimized and you’ll be able to get a decent idea on what kind of hardware you’ll need.