Kolinsky sable is the gold standard for miniature (and watercolor) painting brushes, but there's a range of options within that material. Series 7s and 8404s are on the expensive side, for sure - some won't use anything else, but it's perfectly possible to get good brushes for far less.
I use Rosemary & Co. brushes, both red sable (
Series 99) and Kolinsky (
Series 33). Consider them, but mainly if you're looking to get a whole set - they're based in the
UK, so shipping is prohibitive on tiny orders. Even so, the brushes are priced such that you can generally still get 1-3 (depending on size)
with transatlantic shipping for the list price of a single brush from one of the aforementioned two lines.
As for sculpting tools, I'm also a big fan of clay/color shapers. I use
these (make sure to get extra firm - they still have plenty of give and you'll barely be able to shift epoxy putties with something squishier), although I seem to recall paying somewhat less for them...
I have a set of metal tools, as well, and a few odds and ends that can work for certain tasks (ball-ended styli in various diameters, bits of wire, knife blades, etc.), but since getting the color shapers, I've ended up relying on them for probably 85-90% of my work. When I only had the metal tools, I found that, much like files, large sets are a waste - out of a dozen heads, you'll likely find that there are two or three that see regular use. Better to invest in a few quality tools that suit your specific goals/habits/style/whatever.
