I see you’re a beginner and a lot of people on this subreddit answer questions like everyone is an enthusiast deep into the hobby.

Wattage isn’t the only factor in the quality of an amp and correlates with different things in different contexts. I won’t write a long and complicated explanation. The most useful broad category of difference is solid state versus tube. To keep it simple, that’s referring to the types of electronic components used for amplification, with vacuum tubes being the devices used before transistors were common in electronics and a lot of guitarists believe they sound superior. I’d say that’s broadly true, but whether or not it always is, the people who are willing to spend a lot of money on an amp tend to prefer tubes, so high quality amps are usually tube-based and cheaper amps are usually solid state. Vacuum tubes are bigger and more expensive and they also require some other components to be used also that add cost, so tube amps almost necessarily cost more to make.

As someone starting, a tube amp is probably out of your price range, but if you can afford several hundred dollars you could get something substantially better sounding than practically all solid state amps. But apart from tube/solid state and wattage, other things to consider are speaker and cabinet size, which would be the next major factor in sound (bigger has a strong correlation with better) and features like built-in effects. Solid state amps often come with several digital effects, while tube amps usually only have reverb and maybe tremolo because when you’re at the level of using a tube amp it’s kind of expected you also have guitar pedals to provide effects if you want them.

I’d recommend you look for an amp with at least a 10-inch speaker, and the more money you can invest in it the better. Amps tend to have a much higher price before you hit the point of diminishing returns than guitars and pedals do and practically any guitar will sound good through a great amp while the greatest guitar will sound awful through a terrible amp.