5160. There's MORE than enough for everybody, and it's everywhere! It might not finish as nicely as some steels, but it's just as good as the design, heat-treat and edge geometry. It's a good beginner steel, it demands little, and nicely rewards some skill. While I think 52100 is better, it's not usually as easy to find, or work down.
For a stainless alloy, it would be 14C28N. It's a good all-around steel, easy to get really sharp, holds a decent edge, and it's actually tough for a SS.
I have blades in properly done D2, Bohler K110, M390, VG-10, S35VN, ATS-34, 154CM, CPM154, Magnacut, ZDP-189, N690, 12C27, 14C28N, 440A/B/C, 420HC, AUS-6, AUS-8A, 8CR13MOV, L6, SK-5, 0170-6C, 1095, 1095Cro-Van, Carbon V, 52100, and 5160. They're all usable, but you have to tailor expectations with some knowledge. I also have some damascus, and a few lesser quality Asian steels. The former get little, or no use, because, well, damascus. The latter get little use because they're cheap crap. But, I generally carry a folder in M390, and a fixed blade in Magnacut. I have several blades in S35VN, not because I particularly like the steel, but because I like the designs.
Blackie Collins gave me some advice about 40 years ago, and it's kind of become a mantra after all this time. While not every steel will make a good knife, there's really no such thing as a bad blade steel. If it can be hardened to about 55-RC, or so, it can be made into a perfectly serviceable blade, as long as the maker does his job, with good design, proper heat treatment, correct edge geometry for the intended use, and a competent user who knows how to use that knife properly.