Depends upon your situation. If car camping, weight is irrelevant, so stainless is quite adequate and probably the cheapest.
If backpacking or any other situation in which weight is significant, you will choose between titanium and aluminum, Light weight aluminum is very close to titanium in weight and much cheaper, but titanium is very strong and light. Thin aluminum will dent on you. I have worn out an aluminum cook set, but it took thirty-five years of regular use (the surviving pot waters my doggie in retirement). I still use an army mountain cook set, made in 1951, for large groups (four or more) - two two liter kettles and a stainless lid/fry pan. My favorite for solo or for two is a Trangia 28 cook set - 0.7 liter bowl with lid/fry pan - light and cheap. I am working titanium into the rotation. I splurged on a peak 700 cup which nestles around my water bottle. I carry it routinely on day hikes and can use to boil water and cook if delayed.
There are many fine cook sets on the market, with many features. Many hikers favor the Wally world grease pot and aluminum mugs.
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Geezer in Chief