QuestFind Item required to unlock: Find 5 magnets by arranging Long-Term deals at the Stone Processing Mill Find 5 Telescopes by arranging any deals at Hotel Find 3 antennaes by arranging Long-Term deals at the Lumber Mill
In most situations, starclay is not easy to produce. You need to have a number of sand pits and marble mines to produce starclay. And don't forget you also need cut marble.
Since it doesn't produce starclay in high amounts, it is not advised to order deals on Dish Shop or any other starclay-cost buildings that generate gold, such as Caravan and Sculptor except if you want to complete quest referring to those buildings since you are netting negative amount of gold because the gold cost to produce items that are needed to produce starclay costs much gold than the gold generated by these buildings.
Building decos made of starclay is not advised, unless you need it, since it costs a lot starclay for low happiness cost.