Right then plans of the action.
Information we have gained tells us that Lin can research how to restore the Eldar Pantheon, doing a specific god would help more, but he can do in general as well.
As such I would like to propose that in addition to the Self, the War of Scales and researching the Phoenix Avatars, we should figure out how to restore Lieath and and Vaul.
Lieath is their goddess of fate, her avatars are all diviners on the same level as Ridcully, while Vaul is their crafter god whose avatars are all transcendent level crafters, either one of them restored would likely represent a vast boost to their power.
Other gods would be useful like Kuranous who was Isha's companion and their god of the hunt, Hoeth their god of magic, knowledge and wisdom and Loec who would presumably assist Cheogorath.
Aside from that the Eldar would also appreciate Ridcully's aid in obtaining Anaris, the ultimate blade Vaul forged to give to the Phoenix Avatars, which given the likely power of the artefact we should probably do ASAP.
There maybe other Eldar gods that Durin's created they may wish to prioritise, but these are the ones we know of.