When shopping for an amp, price should not be your only consideration. Some lower-priced amps offer admirable sound, while you may find some costly amps unsuitable for your needs. To judge quality, read user reviews on various guitar websites. You can search some guitar lovers forum to see which amp is much appreciated. Do your research and make an informed decision.
Determine wattage that you need.
Amps are rated by wattage rather than physical size (although high-wattage amps do tend to be physically larger).
Lower wattage tube amplifiers will tend to create harmonic distortion at lower volumes, which is preferable in practice, studio, and miked stage performance.
Higher wattage tube amplifiers will distort at higher volumes–which require more creative mixing for live situations. Further, perceived volume for amp wattage is at 1/10 the wattage and 1/2 the volume. For example, a 10 watt amplifier scientifically half as loud as a 100 watt amp, although the human ear doesn’t perceive it this way.
The wattage and cost of an amp are rarely related, as 10 watt amps can be two, three, or even ten times the cost of a 100 watt amp.For most beginners, a 10 watt amp will be more than enough for a small bedroom. If you are planing to play guitar in a large room, a higher wattage amp is needed.
Now let us focus on channels.
Every amplifier will have at least one, the clean channel designed for outputting the sounds accurately without distortion.
Most will also have a dirty channel, which adds distortion to the sound. Some have a third channel that adds more distortion though these tend to be the more expensive models.
For most guitarists two channels would be a good choice. This way you can have a crisp clean sound or a distorted one and easily switch between them without needing two amplifiers.
Decide which amp you shoud buy by the music type you play.
Before landing on your final choice of guitar amp. You must think of the type of music you play, and decide which type best suits your needs. It is very possible to find a good quality guitar amplifier, regardless of the brand name and type.
Remember to try out many different models and brands before choosing a specific one. I have known guitarists that prefer a certain tone and type of amplifier that I would never personally buy. Each person has their of flavour of sound that they like, and you need to be the one to decide which is yours