[Managarm]

Astral path seems a good candidate to Marignon since their initial sites add +4 Fire gems and +1 Astral gem per turn, and it is very good in the long run.

A high Astral rating also unlocks their mighty National Summons, although some Arcane Probing (Evo 2)/site searching should be done beforehand due to the high number of gems required per summon.