hy tooling costs, especially for long setups, should be <5%
general turning should easy target <10%, and general milling <20%
there are some shop owners that do always consider tooling costs, and try to get a better deal ... and there are few others that know that tooling cost is not the major priority, and some of this very few analyze the unitar costs / time unit / each cnc, even if they have plenty
a negative polished insert ( or a sharp edge type), requires less cutting force than a positive insert with similar nose radius
the chipbreaker geometry also has an influence on the cutting force, thus is not only the positive/negative type as a major rule
to get started on a lathe, just get a box of w rad0.8, v rad0.4 and maybe v rad 0.2 for smooth finishes, and cut off width 2.5 - 3 + maybe a set of hss drills from your local weekend marketAny advice would help
along the way, depending on your needs, get some vhm drills, id tools, threading inserts ( maybe partial profile to cover a wider range); for short id turning, consider also u-drills, since their inserts cost is affordable, they allow stable boring depths of 5d, and most of the times they are coolant through
good luck