Photoline is a cheap-ish image editor (59 euro or $64) and has close to the same features of photoshop and sometime surpases it entirely. Also its layer system operations are blazingly fast (unlike most of the free/cheap software out there)
Photoline is a pretty solid photoshop replacement worth looking at.
Manga studio is very good too.
If you're on Mac Serif has some new apps that have been getting traction call affinity designer and affinity photo.
Check Paint storm studio for natural media brush stuff