We present chemical abundances for 21 elements (from Li to Eu) in 150 metal-poor Galactic stars spanning -4.1<[Fe/H]<-2.1. The targets were selected from the SkyMapper survey and include 90 objects with [Fe/H]<=-3 of which some 15 have [Fe/H]<=-3.5. When combining the sample with our previous studies, we find that the metallicity distribution function has a power-law slope of {Delta}(log N)/{Delta}[Fe/H] = 1.51 +/- 0.01 dex per dex over the range -4<=[Fe/H]<=-3. With only seven carbon-enhanced metal-poor stars in the sample, we again find that the selection of metal-poor stars based on SkyMapper filters is biased against highly carbon-rich stars for [Fe/H]>-3.5. Of the 20 objects for which we could measure nitrogen, 11 are nitrogen-enhanced metal-poor (NEMP) stars. Within our sample, the high NEMP fraction (55 per cent +/- 21 per cent) is compatible with the upper range of predicted values (between 12 per cent and 35 per cent). The chemical abundance ratios [X/Fe] versus [Fe/H] exhibit similar trends to previous studies of metal-poor stars and Galactic chemical evolution models. We report the discovery of nine new r-I stars, four new r-II stars, one of which is the most metal-poor known, nine low-{alpha} stars with [{alpha}]/Fe]<=0.15 as well as one unusual star with [Zn/Fe] = +1.4 and [Sr/Fe] = +1.2 but with normal [Ba/Fe]. Finally, we combine our sample with literature data to provide the most extensive view of the early chemical enrichment of the Milky Way Galaxy.