Skip the grocery store. If it’s on the shelf there, it’s OLD. Most coffee nerds try to stick to beans that have been roasted within the month, give or take. Personally, I live in the boonies, so I buy my beans online, but I stick to roasters in my region - trying to keep it as local as I can.
Some people will recommend sticking with one particular roast and repeating until you get it right. That sounds great from a scientific mindset, but taste isn’t scientific, it’s subjective. While I prefer certain things, I learned a lot about what I like by trying a bunch of different roasts. I drink about two bags a month and I get rotating subscriptions from two different roasters.
As far as gear goes, I will say that you probably want to upgrade to a bottomless portafilter so you can identify channeling, get a cheap scale so you can see what your extraction is, and maybe a WDT tool (diy or cheap is fine).
Yep. It helps cut down on channeling. The more evenly the puck is extracted, the better your shots will be.