sonoko
It's actually not as big of a deal as people make it seem, far too much gearfagging for what it's worth. If you get any camera from the past 10-15 years it will serve you perfectly fine as a beginner, especially if it's one with swappable lenses. You can just get one used and play around with it. None of the details really matter at all as a beginner (in my opinion at least).
The only thing that does matter a little bit is what you primarily want to take pictures of, which will end up deciding how you value the aperture and focal length of your lens(es):
aperture is how big the hole in the lens is, smaller number equals bigger hole and makes the background more blurry
focal length is how "zoomed" in the picture is, more zoomed in generally looks nicer and lets you take pictures of things from farther away, but ends up having a smaller aperture (so darker image)
Those too things plus shutter speed (how long you let in light, so the tradeoff between more motion blur or darker image) will decide 70% of your image result, 29% will be from the lens more generally (how it's built will affect the image, they get really expensive for the fancy ones) and the last 1% is for all the true gearfagging like your sensor size or whatever.
