I have had the opportunity to shoot quite a variety of cartridges over the years and owned a few different ones too.
My current stable consists of 22lr, 20 Tactical, 222 Rem, and a few deer legal ones.
I am soon to change the 222 for a 223 (to get all cartridges in Sauer 202’s) and add a.17HMR.
To answer your question some of the smaller .17 and .20 cartridges are fairly frugal powder wise. Performance wise I have found mine doesn’t quite match the stated US speeds but, I can still get a 32gn bullet well over 4000fps. If I was starting from scratch I’d go with the 20 Practical which is 223 necked down to 204. So you just use a 223 bushing die. As it was I got dies, brass and bullets as part of the deal, although I have found I can form brass with the dies I have too.
It does depend on how far down the rabbit hole you want to go, but there’s a lot of small calibre cartridges to choose from. They are popular over the pond for the likes of Prairie Dog shooting where long range and lots (hundreds in some cases) of shots are fired per day. Low recoil and heat in the barrel are a couple of the reasons for the popularity.
I have a book called Terrific Twenties by Richard Kindler (iirc) that covers many of the 20 cal chambering’s available. It’s interesting reading, with some fairly wild ones in there too.
I am not going to tell you which one is best, I haven’t tried enough to make that choice myself. However I would think VarTarg 20 Practical, Tactical or 204 Ruger would fit the bill.