GP's oranges are not just a funny joke
Now I already knew that a lot of things we take for granted now a days used to be really rare and expensive luxury items in the past, just basic sugar was an extremely expensive item that had to be imported over long distances.
But I was thinking about GP and Bilgewater and I decided to put what I believed to the test and looked up oranges on wikipedia and other sites, but I'll go ahead and post an excerpt from the wiki site since it's short and to the point.
In Europe, citrus fruits—among them the bitter orange, introduced to Italy by the crusaders in the 11th century—were grown widely in the south for medicinal purposes,[6] but the sweet orange was unknown until the late 15th century or the beginnings of the 16th century, when Italian and Portuguese merchants brought orange trees into the Mediterranean area.[6] Shortly afterward, the sweet orange quickly was adopted as an edible fruit. It also was considered a luxury item and wealthy people grew oranges in private conservatories, called orangeries. By 1646, the sweet orange was well known throughout Europe
So if I were to guesstimate how things work in Runeterra relative to our world then oranges likely come from Ionia and Bilgewater, being a port city, likely sees imports from Ionia like oranges, but they're also likely expensive to purchase. So Gangplank having access to oranges all the time is a sign of his power and wealth, he uses them not just for eating but also for his torture.
http://4.bp.blogspot.com/-e5WSglbbjus/VZwl1LybwrI/AAAAAAAATRQ/RnYMJsRSH6k/s1600/GP_Splash_WP.jpg
This is kind of like torturing a man with devices made of gold just to show how wealthy you are.
Further, in his splash we see this.
After his near death experience he's likely resolved himself to have to go through hard times to get back to the place he once was and so niceties like fancy clothes or oranges are things he must discard and so we see him crushing an orange.
has oranges to prevent scurvy. Scurvy is caused by vitamin c deficiency, and it was at one time common among sailors, pirates and others aboard ships at sea longer than perishable fruits and vegetables could be stored. It was one of the limiting factors of marine travel, often killing large numbers of the passengers and crew on long-distance voyages, but it can be prevented by a diet that includes vitamin c rich foods such as oranges and lemons.
