Personally I’d get Lavazza or Ily (in bean format) to get started. Its good middle of the road, its also widely available and consistent. Use that to get good at making coffee with your machine – then start buying other stuff and see how its different and use those differences to guide you towards what you prefer. Buy different new beans before the old ones have run out and then you’ve got better comparisons to make.
Buying beans from a local cafe you like is an idea – but don’t get carried away, they’ll have chosen the beans to suit their kit, what tastes great when they make it might not work out when you make stuff yourself with it. Fell for that recently when had a particularly nice cup from a local cafe – asked to buy some of the beans and they offered me about 50gms in a little paper bag. Wanted something bigger and as they didn’t have any other paper bags ended up walking out the shop £20 lighter with a 2kg catering bag under my arm. Couldn’t get a good cuppa out of the stuff to save my life, although trying to improved my coffee making a good bit.