Very interesting question, especially because the answers necessarily will be very personal, so thank you
@Bobby Tingle for starting this thread.
The pictures you want to make, ideally determine the choice of equipment to do that. That sounds very much like what the teacher wants to hear from his pupil and of course it doesn't always work that way. In my long photographic hobby history I didn't have a clue what I really wanted to do, and now that I'm a little further I seem to have slid into a very narrow field ( or dead alley?
) of making street stills. And that largely dictates my lens choices, for instance. Gone are the days where I took the Sony FF wide/standard/telephoto F4 zooms with me. The last half year I just took the Sony A7R2 with a Zeiss Loxia 2/35 and 2/50.
I'm in the fortunate position that I can spend enough money on something photographic. I won't just flaunt my Euro bills around but if I really, really want something, I buy it. Latest example: Voigtländer presented us with a native FE 1.2/40. A while ago I told my wife I had an awful lot of 35mm lenses (Sony FE 1.4/35, FE 2.8/35, Zeiss Loxia 2/35) for someone who doesn't really like that focal length and that I owe it to myself to get a native FE 40mm now that Voigtländer has one in the program; 40mm feels right to me, period, always had that experience. I decided to sell off the 1.4/35 monster because I hate its size, moreover I really didn't need such a fast lens. I also sold my adapted Olympus OM Zuiko 2/40; the latter one not because it's not as fast but because I really like the convenience of having the EXIF data in the raws without any hassle. The Voigtländer 1.2/40 max. aperture is a nice bonus but I would have happily settled for an f/2 or f/2.8. I simply let time decide how the usage patterns will develop, I can't say which lenses will stay or go, and in fact it has always been that way.
As a side-step, money is an important parameter in our hobby for a lot of us, but it often is about what we think we should or shouldn't spend, not what we can or can't. It's about personal or family priorities really. For instance, I can't bring myself to spend 20k€ on a car even if my bank account would allow for it, while others will happily do that and cap camera purchases at € 500. As I said, personal priorities. My best purchases have been the ones that were conscious, sometimes long-whining decision processes; coincidentally these purchases were mostly not on the cheap side, as you can see from the stuff I already mentioned.
Well then, let's cut to the chase: what do I look for in gear?
1. Image quality
This is key for me. I wasn't happy with µ4/3 and the jump from the Panasonic GH2 to the Sony NEX-6 provided a big improvement in dynamic range, resolution and noise performance. Enter the Sony A7 late 2013; I immediately went for it, also with the idea of using my Minolta lens collection to its full potential. Again a big step up in image quality. Then came the A7R2, primarily to get rid of sensor reflections and now I feel I have a camera that provides the finesse I want. I have thought long and hard about getting a Fuji X100F for street photography and tried one out at a fair, taking home the raws for further processing. And I'm pretty sure I would have been confronted with way too many occasions on which I regretted not taking the A7R2 instead of the X100F. And upon that insight I took our household scale up to attic and weighed my bags and quickly discovered that my favorite bag is over 1 kg! That same day I bought a small CaseLogic one of only 300g. That's a difference of 2 Loxia lenses! Moreover, I didn't have fun with the X100F, simple as that, it's just not my type of camera. And see point 4: I'm a one-system guy! That put that idea solidly to rest.
2. Must be a joy to use
Best example: the Zeiss Loxia lenses. Smooth-silky focussing, no sideways displacements of the viewfinder image during focussing. You immediately see what the lens is set to, no clever operating mode will disturb that. Image quality is superb too. Yes, even that of the Loxia 2/35. Pixel-peeping at 200 % on my iMac 5K screen will reveal defects but if I just view an image at a full-screen image of 50 x 33 cm I must look carefully for those defects. Mostly the decision to use f/2 is wrong for other reasons, mostly too little depth-of-field.
Is the A7R2 a joy to handle? Errrm... let's say adequate. I could think of a few simple UI changes that would make it way more enjoyable. Some of them are offered in the Mark III successor but I plan to at least hold off until the Mark IV series comes along. Would Fuji for instance offer me a better user experience? Most probably, but you'd have to drag me kicking and screaming to give up on 42 MP FF. Point 1, remember?
3. I want my bases covered.
For instance, family is an important part of my life so I want to have the gear to adequately cover a day out. That means I'll keep the native AF zoom lenses, even if they mostly gather dust.
4. I'm a one-system guy.
I have had multiple systems alongside each other on various occasions in the past, the latest iteration being the Panasonic G and Sony E system. I ended up invariably selling off the second system. I just can't bear switching between different camera systems. I admire people that will take a µ4/3 camera one day and a Sony A7R2 the next day.