Look into your budget and work from there. Get a basic setup, learn along the way until you hit limits and upgrade from there. The latest models offer the newest bells and whistles but they are probably unnecessary from beginner pov.
( pic from dpreview )
DSLR vs Mirrorless cameras. Mirrorless is more compact, and is the future moving forward so you probably do not want to get (used) dslrs although they do offer incredible value. Used gears that are one or two generations earlier can be great bargain but with the downside of breakdowns.
( pic from dpreview )
Sensor sizes :
In general, larger full frame sensor cameras offer technical improvements over smaller cropped sensors but that does not translate exactly into real world mind blowing differences in image quality, so if budget is a concern, apsc size cameras are ok too. Composition and processing has a far greater impact.