Knowing what will have the biggest impact on your image quality is hard, as it varies so much from genre to genre. For still life and food photography, this is the order of importance I have come up with.
This video discusses how to prioritize spending money when you are ready to begin upgrading lights, modifiers, cameras, and lenses. Although there are lots of throwaway sayings about investing all of your cash into lenses that get banded about on the internet, this isn't always the best way to go. By breaking down the genre I work in, I was able to find the best areas to spend my hard-earned cash on.
I will start this off with a small disclaimer: I shot on crop sensor cameras with cheap lights and modifiers for a good six years. I still got paid and made a living from photography, and some of those images are still in my portfolio. It took me over a decade to collect all of the gear that I currently have, and I did so one item at a time. There is, of course, a huge amount I still want to upgrade, and I use the method discussed in the video to decide where to put my money.
There are loads of sites and channels that offer advice on technical image quality when it comes to cameras and lenses; however, there is much more to how good an image looks than sharpness and dynamic range. A lot of what these websites don't and can't discuss comes down to aesthetics and taste. The more important metrics are qualitative rather than quantitative for a lot of genres of photography. Working as a commercial food and still life photographer really brings this to light.
How do you prioritize your new photography purchases in your genre?
I always recommend upgrading your computer first. Most photo gear is fine until it is not and you will know when it is not, but it can be so easy to just slowly let your computer get older and older and with every passing day your workflow gets slower and slower which has a direct correlation to your efficiency and thus your profitability.
I'd say get some decent lights and modifiers first and study light and composition, then upgrade to at least one quality lens and if you have the will/cash upgrade your camera body. If you have a camera that is one of those with over a zillion megapixels or you plan to shoot video then I'd say fit in a decent PC upgrade with a Ryzen7/i7. Even the newest Ryzen5 would be pretty good. It beats out my Ryzen 7 2700 by a lot and currently most Intel processors for around $150. It's amazing. I wouldn't worry about GPU upgrades unless you edit video or play games.
For food/still life: lighting, including modifiers. Good light will help a mediocre lens and camera by a lot; the best camera and lens won't help poor lighting, again...ONLY relative to food/still life.
I think your suggestion works for most forms of photography. Especially portraits. I can make a great image on a D100 with and 18-55mm lens if I have good lighting.
I included the disclaimer because for some kinds of photography, good light really means appropriate light, and often, not something you can upgrade. :-)
Definitely true. That is much better perspective of looking at lighting. :D
Upgrade whatever needs upgrading.
https://i.imgur.com/aIDbYsS.gif
You need to upgrade whatever is causing you extra hassle and distracting you from setting up and taking photos, and then editing them. From a tripod leg or knob that's not working very well, to worn velcro on an egg crate--if you're constantly having to worry about your equipment, or worse, if you're like me, problems with equipment cause you to get annoyed and distracted--you need to fix that now and buy something that does work for you. As for cameras, I only upgraded to more megapixels because I needed them to work with in post-processing. Let your annoyance meter be your guide.