What camera should you buy? Great question! It's a question I have no answer to, only because its very subjective and in 2020 there are a lot of great cameras. But if I had to name one it would be Sony Alpha A7. And no, I don't use it. I use Nikon D4, primarily.
Don't chase the latest camera, pick a system (Canon, Nikon), get a decent camera, and invest in lenses.
Robert Capa once said: "If it's not good enough, you're not close enough". So get close to your subjects.
Photograph on aperture or shutter priority when starting out, and after some time try manual mode. Learn to see what aperture and shutter speed does to your images. Once you are comfortable with manual mode - it should be you main mode most of the time.
Slow down. Think about what you want to achieve with them.
Try different angles: low, high, weird. Anything that will make a photo more interesting and unusual. It may work or it may not.
Learn the rule of thirds and other compositional fundamentals like leading lines, angles, foreground/background.
Learn how to use a flash.
Use a tripod for landscape photos.
Environmental portraits should have the environment as part of the story. Make it interesting.
Experiment with 'bulb' shutter setting. Doing this at night in the city will make interesting images.
Use a reflector for portraits outside to fill in the shadows.
More to come / work in progress...