Some local food worth buying in Culion:
The famous bolpen. If there’s no stock in Culion, try the port of Coron where it sells for P90 per pack. Just make sure it’s packed properly in newspaper and plastic lest the stinky smell follow you to the van, all the way to the airport and home.
Casuy (cashew), the curved nut is sold roasted or in various sweet formats. My favorite is the Casuy Brittle I found in the airport. Order these days before leaving the island and buy it in Culion where it is cheaper than in Coron, and costs only a fraction of the price in Manila.