After you've taken an image on your camera, and you can view it on your rear screen, you should be able to press an "info" button or something similar, to cycle the information shown about the photo you are viewing. It varies camera to camera, but pretty much every dslr should have this feature and it should allow you to view a histogram of your image.
This link has an example of how histograms may appear
https://i.pinimg.com/originals/2c/ce...5834a25a29.jpg.
The histogram can show how much of your image is exposed to what amount.
Since most of the night sky, generally speaking, is dim/dark, trying to aim for an exposure with a histogram thats slightly left of center as a good starting point.
If the histogram peaks to the far left, try capture more light with a longer exposure or faster f/ ratio (like when using a focal reducer).
You may not be able to get exposures long enough to achieve the histogram you are aiming for, but just do the best with what you have.
Dont worry so much about purchasing new equipment, get the feel of what you currently have first. A bahtinov mask will be very helpful though, as will a focal reducer.
Colimation can really help get finer details, but if an out of focus star in the middle of the view shows a concentric donut its probably close enough not to worry about for now. Collimation wont help much if focus is off.