I’ll keep this brief and as too the point as I can, with what I think are the most important factors when picking your first camera!
Budget
This is something that only you will know for sure. Generally, the more you spend, the better the camera…
DSLR / Mirrorless / Bridge / Compact
DSLR (digital single-lens reflect – whoever actually cares!) cameras are the most common professional cameras. They have the ability to change lenses which is great.
Mirrorless cameras use newer technology than DSLR as the viewfinder (if present) is digital whereas on a DSLR you’re viewing through the lens directly.
Bridge cameras have functionality like DSLR and Mirrorless cameras but you cannot change the lens.
Compact cameras are the generic point and shoot type cameras that don’t tend to have the same functionality as the other categories.
Sensor
I would recommend having buying a full frame camera over a crop sensor camera if funds allow. There is a noticeable difference in image quality. The downside is that the cameras are larger and the file sizes can be much bigger.
Brand
I love the Sony camera line up and I have been using Sony cameras for 6 years now. Before that I was a canon user and took some great shots with my Canon camera. From the brief experience I have, I would recommend Nixon over Canon but in reality I would recommend either. Not because they’re bad cameras but because I think that Sony / Fuji cameras are better even if they are less of them sold per year.
Useage
I look for a camera that can be used for all types of photography but if you’re looking at a specific use, there maybe a clear winner. I recently purchased a Sony A7R IV and although I love the functionality and images, the file sizes are far too big for my storage setup. I didn’t realise how quickly my space would disappear with 64mb files (I know that I should have though).
Lenses
This is perhaps more important than the camera itself. The lenses can cost significantly more than the camera body and the difference in photo quality by changing away from a stock lens is unreal. I have a collection of lenses but typically I purchased used lenses.
Some links:
Camera/Lens rankings: https://www.dxomark.com/Cameras/
Sensor Sizes explained: https://www.theschoolofphotography.com/tutorials/camera-sensor-size-comparison
Mirrorless vs DSLR: https://www.tomsguide.com/uk/face-off/dslr-vs-mirrorless-cameras