Ah, wheels. So much information...
Want to make it easy? Just grab 52mm-54mm in your price range.
Want to get more into it? There's extra info below!

The most popular wheel sizes are 52mm, 53mm, and 54mm.
Some will prefer a smaller wheel for weight reduction or having a lower feel to the ground. But with a smaller wheel you are sacrificing durability.
A larger wheel will weigh more, but will be overall faster and a longer durability.

Smaller wheels will give you a faster acceleration while a larger wheel will give you a faster top speed. 53-54mm is in the middle with a nice acceleration and top speed.

Skateboard wheels use a durometer scale to measure shore hardness. Think of it as a hardness percentage.

78a - 87a = Soft and grippy. Great for longboards and cruiser setups. Quiet and smooth!
88a - 96a = Harder and faster than the previous listed durometers, but still soft enough to cruise over bumps and cracks. Great for beginners too!
97a-98a = Pretty hard, but not ankle rattling hard! Gives you some vibration reduction and acceleration on sidewalks. You might have to try a little to get them to slide.
99a = One of the most common durometers and harder than the rest. Some say it's perfect! High durability, high slideability, high acceleration, but you will have your speed stolen from you on rough patches of concrete. Suggested for street and park skateboarding.
101a = The ankle rattlers! Very hard wheel. higher durability, higher slideability, higher acceleration on smooth surfaces. Suggested more for smooth skateparks than street, although some people prefer the very hard feel and sound in the streets.
83b - 84b = Oh man! The controversial B durometer scale! Harder than the A scale, but if you get to the 85b and up range, the wheels start to feel a little plasticy? 83b=103a, 84b=104a. Usually higher durability, slideability, and acceleration than the A scale.

A narrow wheel will feel lighter, slide better, and give your trucks more room to grind at the expense of lower durability.

A wider wheel will add weight, feel more grippy, and take away some of the room on your trucks to grind at the expense of a higher durability.

Some will prefer a lighter setup and others will prefer more heft. This is all a personal preference that is developed with time and experience. Always try different things!

A higher wheel cost usually means a higher grade urethane was used to increase durability. If you are an experienced skateboarder (RIPPER) and hard on your wheels, it might feel like you are forced to ride a higher grade urethane that can put up with your abuse!

You do not need a premium urethane wheel if you are just starting. Go with what is in your budget!