I think the question really is quite complex. It certainly is to me. There are so many variables.
When I started out years ago, I whacked a home made antenna up in the loft and connected it to the cheapest DVB-T stick I could lay my hands on with a spare piece of satellite cable. I was perfectly happy with what I got but like so many pursuits, you sometimes don’t realise what you are missing out on or how little you know about the subject for a while.
As @foxhunter says, you can compare your results with those of other feeders but that doesn’t tell the whole story. Take mine for example, https://flightaware.com/adsb/stats/user/technodevotee#stats-100624. The problem is that you can’t tell from the information there what gear I have or how many 'planes actually fly through the airspace ‘seen’ by my antenna.
I can tell you that I have two home made 1/4 wave ground plane antennae (spiders), in the loft right up under the ridge tiles, one on each side of the house. Each of them has an RTL-SDR triple filtered LNA underneath and that is connected to an RTL-SDR Blog V3 dongle.
I’ve gone though all the gain settings over a the last year to find the setting that gives me maximum range, positions, aircraft etc. and I settled on a gain of 38, which I reckon it is about as good as I’m going to get with my setup.
I could probably do better with a proper antenna and better cable but unless you are a perfectionist with an unlimited budget, you have to stop somewhere.
Even If I was a perfectionist with an unlimited budget, like most people there a limit to what I can do. Short of moving. As much as I’d like to, I can’t cut down other people’s trees, demolish other people’s houses or remove the hills that are in the way of my view to the horizon.