As far as I understand, contact lenses should always be chosen with a prescription. You should have a prescription for lenses, not glasses. This rule should apply to both the first purchase of lenses and subsequent ones. Some online stores of means of contact correction, for example, I am SPAMER, provide the services of an ophthalmologist who will help you figure it out and professionally prescribe the parameters.
Do not violate the instructions for using these products, take care of them and, most importantly, do not prolong it, and everything will be fine.
I answer as a wearer of contact lenses.
You should definitely consult a doctor, since the eyeball has a radius of curvature that you cannot determine on your own. Also, the doctor will help you put them on for the first time, I was given one-day "trial" lenses for free.
The first dressing for me personally was a nightmare - after all, the eye was not used to being poked with a finger and straightening something else there - but nothing, skill and habit comes with time, the first times I put on a lens for about 5 minutes, now (I have worn more than a year) less than a minute.
Pay attention to the moisture content of the lens. The higher the better for the eye, the same applies to oxygen permeability.
If you mainly work at the computer, then by the end of the working day you will feel discomfort. Accept, this is a lack of contact lenses, stock up on drops, it will be easier.
An important point is not to put the lenses inside out. You will see the same, but the eye will be unbearable to cut - the edges of the lens are sharpened for a perfect fit, and when turned out, the edges simply cut into the cornea.
You shouldn't save on the first lenses, let your eyes adapt to a foreign body, then you can choose the best price / quality option. Personally, only silicone hydrogels are suitable for me, other materials cause significant discomfort.
I myself wear two-week lenses for three weeks, until unpleasant sensations appear, while I follow my hygiene very carefully, so it turns out to save a little.
After consulting with an ophthalmologist. He will tell you how to put them on and keep them clean, what diopters are best to choose. When choosing, there are some individual features such as curvature (if roughly, the diameter and angle of the lens curvature) - your eyeball may be smaller and then you need a non-standard value - this is not uncommon, you just need to pay attention to this figure when ordering lenses. Well, I would try several brands to understand which one suits you best. If the lenses are uncomfortable to wear, then they do not fit, this is very individual.