What do you usually upgrade first - cartridge or phono stage ?

I think that's a difficult thing to generalize in such a way. The last time I upgraded, I upgraded my cartridge to a much higher level. Later I upgraded my phono-stage, but that was because I added a second tonearm and needed two inputs. The phono-stage upgrade was great for the cartridge upgrade but not necessary for that reason alone.

It'a about striking a good balance in the end. There is no good rule of thumb.

dwette, could you post what you upgraded to what ? And what turntable/tonearms do you have ?

What, only one or the other? Not a few of each at once? That’s way too little chaos for me to enjoy a hobby with...

If you have one egregiously below level of the other, then do that one. Otherwise, get which you fancy more; it doesn’t really matter. New cartridges are probably a better dopamine hit (on average) but phono stages can stick around for multiple carts, don’t need alignment, and don’t wear out (so much). 

A few of each at once, right.

New phono stage can bring out everything your old cartridge is capable of, and new cartridge will likely sound better than the old one with the old phono stage.

The world's best cartridge will not sound great with the world's worst phono stage but budget cartridges will benefit from the world's best phono stage. Best to buy the best performing phono stage you can afford and work your way up to a cartridge which equals the the phono stage.

Before cartridge and phono stage get the best turntable and arm you can afford. Buy second hand if prices are intimidating,