When I moved onto all grain brewing the standard for starting up quick was a 5 or 10 gallon, round, Rubbermaid or Gott type cooler. I worked through 2 - 5 gallon coolers and 2 - 10 ten gallon before I settled on a rectangular cooler (blue, of course. Old forum joke). The round coolers all suffered heat stress breakage.
I started with .5" copper pipe, that I slotted, by hand to build a mash filter. Modified for each cooler I switched to. Then I found Denny's SS water supply line cover idea and switched yet again. Also worked through several sizes, lengths and whatever else you can think of.
I also moved though plastic valves, brass valves and SS valves.
My progression through options seems a bit over done, looking back.
Basically the point of all that is...
You need to make a few decisions about how you want to brew before you can pick you equipment. I'm more of a "I want to try it before I spend a lot of money" type of guy. BIAB wasn't a thing when I started. It was all "real men mash and sparge" followed by a bunch of Tim Taylor grunting.
So I built a mash/lauter tun, got a 12 gallon kettle and took off.
Now a days, if I were starting out I would likely start with BIAB. Spend a year learning the processes and then consider what my next step was.
Buy the largest kettle you afford and comfortably use to start with. Kettles are probably your largest startup cost. Try not to spend it twice.
Get a good propane burner if you can cook outside. Look at induction if you can/have to cook indoors.
That's where I would start today, if I was starting over. And if you plan on brewing, a lot start exploring kegging now, before you have find homes for 25 cases of beer bottles.
Paul