Whether top tier gas is a must depends on the vehicle. I've never made an effort to use it and had no problems but I'm driving decades-old cars, none of them even built in the 21st century.

All the gasoline in a given area usually comes from the same refinery and each brand adds its own additive package. Minimum standards are enforced for gasoline sold in the U.S., however top tier adds higher requirements recommended by auto manufacturers. The leading fuel brands are mostly if not all top tier, but if all you have in your area are "no name" gas stations this site may help you find any top tier gasoline that may be available in your area:

https://stationfinder.toptiergas.com/

There really isn't any way for an average guy to ensure the quality of fuel he puts in his car unless he has a test kit and take samples from every station in an area.

Even if he found a station with the best gas, who's to say it stays that way? We have no idea how well filling station's tanks are maintained and the fuel is tested for purity.

I keep a record of every fill up including name of station, location, odometer reading, trip mileage since fill up, gallons dispensed. Find out your MPG from your last tank by taking miles driven on last tank by gallons used to fill tank back up. For example if you drove 400 miles then stopped at a station to fill it up and put 16 gallons in it from last fill up, you got 25 mpg.

I think the station that dispenses fuel that gets me better MPG has better gas and it's not always name brands. You might also want to try no alcohol gas.  Ethanol is a mandated additive but states permit stations to offer E0 fuel for customers that want it for their watercraft engines or small seasonal engines like snow blowers because the alcohol can separate from petroleum fuel over time and the alcohol can attract moisture. pure-gas.org