This page is a Troubleshooting guide with ways to solve some problems with The Wheels of Lull mod.
Avarri can be extremely bugged and he may not sell anything. You can try disabling - enabling him through console. You can also try leaving the Smithery and return, he will sell things, but this can break the Harquebus list quest! He will be giving you a list of things needed for making different Harquebuses according to your progress through main quest, so better do it in the beginning of the main quest or not at all.
Another workaround is that you can just steal the things from his selling chest, but you need to use the TCL console command to get to the chest. The chest is behind the wall near the smelter.