Hey, optometry student here.
Health providers always need to recommend that you go in for a proper evaluation for contact lenses. I absolutely agree to it’s importance and also recommend that you should visit a local optometrist for this.
However, the reality is that contact lenses are so widely available for purchase online that if you are looking for soft contact lenses (which you didn’t specify which kind of lens you were looking for), people just wanna get them ordered and out of the way. I’m personally guilty for doing this too. So, I think I’ll just help you out with what I know.
From your glasses prescription, usually the numbers under the S column don’t need to be adjusted unless they are a very high value (yours are not that high) and the number under the C column determine if you need Toric lenses (values over -0.75 usually mean you do). Since your C column values are not over -0.75, we do something called a spherical equivalent which adds an extra -0.25 to your left eye. Spherical equivalent basically takes every -0.50 in C and moves it to be and extra -0.25 in S. So, from what I can tell, your contact lens prescription should be: Right eye: -2.25 D. Left eye: -1.50 D.
To answer your side note: No, you don’t have to wear the exact prescription. Although, if you stray too far from the prescription, you’ll absolutely notice headaches, eye strain, and other symptoms of either having too much power given to each eye or not enough to correct your vision.
TLDR; Please get a proper fitting, but if you really don’t want to: Right eye: -2.25 D Left eye: -1.50 D No, you don’t have to wear the exact prescription.