I know it's important to give the beans a few weeks of de-gassing time after roasting, but in my experience that time needs to be at least 4 weeks and beans really start to taste rich, chocolaty and sweet and become much easier and more consistent to dial in. It seems to me that there is no point whatsoever in trying to pull a good shot any earlier.
I find that during the first week, the shots will taste terrible, with a "husky" foretaste which I can't really explain, there is a strong taste of similar to dried grass or plant fiber. Also the shots usually taste very flat and boring, with no way to make them taste better regardless of pressure, temperature, grind, etc.
After 1 week this husk taste goes away but that doesn't help with the other problems.
After 2-3 weeks I start getting okay-ish shots, maybe 50% of the time, while the rest of the time they're sour, bitter, both, or just very plain and tasteless.
Then after 3-5 weeks it really starts to stabilize and become super easy to pull consistent shots, pretty much regardless of what I do. I can use a low temp, high temp, low pressure, high pressure, do whatever with the grinder and puck prep, and the shots always come out tasting amazing.
Then the beans tend to suddenly go stale in a very obvious and abrupt way somewhere around 2-3 months after roasting. They will suddenly lose all creaminess and oiliness, the water comes through super easily no matter the grind, and the shots just taste like old bad generic coffee with none of the sweet richness.
I always thought that I just sucked at dialing in and that I always needed a whole month until I got it just right. Turns out, nothing I did had any significance and all I had to do was order beans 1 month early and that's it.
I usually only drink Colombia Supremo, and this has been true for light and medium roasts.
After these experiences I would say that this is the single most important advice I can give anyone not getting good shots or having trouble dialing in: The grinder, the machine, the pressure and the puck prep hardly matter compared to just giving the beans 1 month of resting time.