The Indonesian equivalent of souvenirs is oleh-oleh. While souvenirs are considered a nice gesture where I come from, they are expected here. Now, oleh-oleh does not have to be anything fancy. In fact, food will do just fine. However, there are two rules intricately woven into this tradition: the first is to buy it, and the second is to buy enough.
Lesson #18: Having enough oleh-oleh is a free pass entitling you to unlimited cabin baggage on Indonesian airlines. The result is an excessive number of inconveniently stowed boxes in the overhead compartment. Sort of like using a giant plate for two green peas.