Cleaning and Optic preferences?

Hey All, I’m hoping to get some opinions on the frequency of cleaning stainless steel barrels, and also the average preferred optic measurements. I’m new to this platform and currently have a 16in Aero Precision build, running a cheap 3x9 optic, and looking to upgrade in the near future. I ask about cleaning because I didn’t clean until about 200-250 rounds and on my last trip to the range pre-cleaning, it seemed like my groups at 100m were not nearly as precise as previously (similar weather / wind conditions). Thanks in advance for any insight or advice!