This is the order I bought my woodworking gear.
1) A 1.5 HP baby combination machine with an 8" Small Table saw, 4" jointer and a doweling able - this is really just a toy. I used it for 20 years before I upgraded - I now run a thin kerf metal cutting wheel in the table saw and that is extremely useful
2) 12" 3HP table saw with cojoined cast iron router table. Router and saw share the same fence. This is a bit of a beast but a very useful machine - I use it a lot to cut ally! I really should not have bought this when I did.
3) 1HP Heavy duty Drill press - this is an excellent machine
4) 10" combo jointer thicknesser - fiddly but excellent
5) 19" Bandsaw - this is what I should have bought first
6) Small 1/2 HP woodworking lathe - this depends how much you want to turn wood
I also now have a bunch of other stuff mostly under restoration including a 16" jointer and a 16" 3 Phase big radial arm saw (which I hardly ever use) .
Here's a pic of my very small shop - the bandsaw and jointer/thicknesser live on the back veranda - they can just been seen thru the shed door. Most of my bigger machines are at the milling yard.
Assuming you already have some hand power tools like a drill and a circular saw, I would recommend that the first WW machine anyone with a mill should buy is a 14" (or bigger if you can afford it) bandsaw. It can be used to resaw milled boards, cuts curves and although it is slow, it is also relatively safe. Then I would recommend a small - maybe 6"? jointer (wider with long bed if you can afford it) and a table top thicknesser, or a combo machine of some king. These 2/3 machines and a bunch of handtools can get you a long way down most projects. Don't forget to get yourself a decent dust extractor as these things make a lot of dust.
After this it depends what you want to do.
I reckon a decent drill press is hard to beat - these things are just so handy.
Then I would say a table saw and a router table.
Other things like linishers, bigger jointers and thicknessers, bigger bandsaw and radial arm saws come well down the list