Amps are one of the most important aspects of playing electric guitar as they amplify your guitar and help to define its tone (even though the guitar itself defines its tone even moreso than an amp does).
When it comes to watts, the higher the number the louder the amp will go. However, if there's a five-watt Fender solid-state amp and a five-watt Marshall solid-state amp, it doesn't mean they'll be as loud as one another as volume per watt can vary from brand to brand. Also, tube amps get louder than solid-state amps of the same wattage. Tube amps can also acheive better tones, but solid-state amps are cheaper and less likely to break when being moved around a lot.
Do keep in mind that not being able to read music does not determine whether or not you will be or are a great guitarist--some ofthe finest musician's can't read music. Tommy Emmanuel is one of the best examples and he can't even read tabs.
As for a pedal, it's a device used to alter some aspect of your tone. Distortion pedals, for instance, distort your tone. Delay pedals, on the other hand, had what most people refer to as an echo. There are hundreds of effects out there aside from those two though--compression, wah, overdrive, reverb and a hell of a lot more. You don't really need to worry about pedals when you first start playing electric though...unless you want to.
As for knowing what amps are and aren't good, the brand name can often be a good sign in either direction. Fender and Vox, for instance, offer great amps--both solid-state amps and tube amps and in a wide array of price ranges. For your first amp, you should stick with a solid-state amp though due to their lower prices and due to the fact that, as I said before, tube amps can be damaged more easily when traveling so they need to be cared for moreso than solid-state amps.
If you want a good first amp, I'd highly recommend the Fender 25R Frontman. It's a 25-watt solid-state amp which comes in a choice of two colors--red or black--and, for $100, it's a great little amp. It's also loud enough for smaller gigs in which there is no PA system so, if you start playng out, the Fender 25R Frontman can pull it off until you can afford a better second amp.
Readig reviews by customers can also be of help when deciding on your first amp, but I strongly recommend that you try anythig before you buy it and especially if it's a guitar, an amp or a pedal. After you try it, however, it's fine to order it online. Down below, I'll share some links to various websites where you can order equipment from and where you can read customer reviews. My personal favorite is Musician's Friend, which will be the first link I include.