Gibbs is a generally knowledgeable person and right-hand man to (Captain) Jack Sparrow, often providing the movie's cast as well as the audience with background information. He is deeply superstitious and makes frequent references to various causes of "bad luck" (e.g. having women on the ship or waking a sleeping man). He is also very fond of his rum, which he drinks from a leather flask. He takes a moment of silence to anyone who gets left behind (especially Jack), but gets over it quick enough. Gibbs is probably the only character who knows Jack Sparrow's history, and has a great friendship with him, being one of the few people to admit he went to rescue Jack from Davy Jones' Locker because he missed him, and being the first one to agree to do so. He and Jack also share a handshake, and would say, in the first and third film "Take what you can - Give nothing back!" Writer Terry Rossio has said he actually considers Gibbs to be the most virtuous character in the series.
In the first film, Gibbs is first seen as a Royal Navy warrant officer (probably the boatswain) aboard the vessel carrying Governor Weatherby Swann and his young daughter Elizabeth Swann from England to Port Royal in the Caribbean. Gibbs is highly superstitious and fearful of the mere mention of pirates. When they come across a wrecked vessel (from which young Will Turner is rescued), Gibbs is the first to suggest it was attacked by pirates. He was likely correct, as Elizabeth witnessed the Black Pearl leaving the scene.
Sometime over the next eight years, Gibbs either leaves or is expelled from the Royal Navy. It is implied that, like James Norrington, he may have been disgraced chasing pirates, eventually becoming one. It's also possible he was press-ganged into the Royal Navy, as piracy offered greater freedom at the time. When Ex-Commodore Norrington applies to sign aboard the Black Pearl in Dead Man's Chest, he tells Gibbs his life is just like Gibbs's own, only "one chapter behind." Gibbs may also have been dismissed from the navy for his drinking, as he is often seen swigging rum from a flask. Despite his initial dread of pirates, he became good friends with one: the Black Pearl's former captain, Jack Sparrow. Jack's history is well-known to Gibbs, including his quest to regain the Pearl and seek revenge on his mutinous first mate, Hector Barbossa. He is also familiar with the curse that has afflicted the Black Pearl's crew and how to break it. He hasn't grown any less superstitious, however, and continually rambles on about what causes bad luck, such as bringing women aboard ships, as well as waking a man while he's sleeping.
Jack finds Gibbs sleeping among pigs in Tortuga after he and Will escape from Port Royal. They assemble a crew to man the stolen navy vessel Interceptor. After Jack falls behind during a confrontation with the pirates at Isa de Muerta, Gibbs assumes command, indicating he is now Jack's (more trustworthy) first mate.
Unfortunately, the Pearl quickly caught the Interceptor and following a sea battle, the Interceptor was destroyed. Gibbs and the rest of the crew (along with Will and Elizabeth) were captured.
Back on Isla de Muerta, Elizabeth freed Gibbs and the crew from the Pearl's brig and they took control of the ship. Although Elizabeth tried to convince Gibbs and the others to save Jack and Will, who were fighting Barbossa on the island, they set sail with the Pearl, telling Elizabeth that Jack owed them a ship. However, they later rescue Jack after he escapes the hangman's noose (with Will's assistance) in Port Royal. With Jack back in command of the Black Pearl, Gibbs stays on as second in command.
In the second film, Gibbs is still serving under Jack aboard the Black Pearl. In the beginning he is singing Dead Man's Chest until Jack comes back with a drawing of the key to the Dead Man's Chest. Jack at first acts like he wants the crew to help him find the key and the chest but when Mr. Gibbs asks if the chest and key is what they are looking for, Jack always answers something like "No" or "You are not making any sense at all". Afterwards Gibbs, Jack, and the crew are captured by a cannibalistic native tribe after they beach the Black Pearl on the mysterious island of Pelegosto. Later Jack becomes chief of the Pelegostos which Gibbs describes Jack's actions of being chief is to actually stay alive from being eaten by the Cannibals, who think he is a god. But sometime later they narrowly escape, following Will Turner's arrival while searching for Jack. He still seems superstitious by nature, as shown when Jack reveals the Black Spot to Tia Dalma. Upon seeing the spot, Gibbs gasps in shock and, in a panic, performs a superstitious ritual where he spits, pats his chest three times, and spins in a circle. Pintel and Ragetti copy him. However, Gibbs seems less superstitious than before. At the movie's beginning, Gibbs sings the shanty, Dead Man's Chest aboard the Black Pearl before Jack arrives in a floating coffin. The song could be a prelude for the movie.
Gibbs accompanies Jack on his quest to find the Dead Man's Chest, containing the heart of Davy Jones, after Jack learns that Jones intends to collect a blood debt Jack owes him. When Jack goes ashore on Isla Cruces, he leaves Gibbs, Marty, Cotton, and the rest of the crew on the Pearl, which, according to the writers, is so they will be spared should the Kraken or Davy Jones attack. Instead, he takes the most dispensable crew members (James Norrington, Pintel, Ragetti, and Elizabeth Swann).
Gibbs is also among the few survivors after the Pearl is destroyed by Davy Jones' monstrous beast, the Kraken, an attack in which Jack is sacrificed by Elizabeth so the Kraken would not pursue the others if he tried to flee with them; thus Jack and the Black Pearl are sent to Davy Jones' Locker. Will, Elizabeth, Pintel, Ragetti, Marty, and Cotton (with his parrot) are the only survivors. When they return to Tia Dalma for help, she asks if they would be willing to do anything to save Jack and the Pearl. Gibbs is the first to accept the challenge.
Gibbs, along with Cotton, Marty, Pintel, and Ragetti, assist Captain Barbossa as they make their way to World's End to rescue Jack Sparrow. When Jack originally wanted to leave some people behind in Davy Jones's Locker, Gibbs was one of the only people Jack wanted to take back to the world of the living. He is one of the very few sailors to put up his hand when Jack asks if any one came to save him just because they missed him, indicating a strong friendship between him and Jack. Jack also lets Gibbs throw his hat - as long as he gets it back.
In the closing scene of the film, Gibbs gets slapped by Jack Sparrow after Jack gets slapped by both Scarlett and Giselle. This is because Gibbs passed out drunk and let Barbossa steal the Black Pearl. Evidently he sleeps with a Teddy Bear made of burlap. Despite falling asleep and causing the Pearl to be stolen he and Jack share a smile, and their toast from the first film, and part as friends. He then stays behind in Tortuga with Scarlett and Giselle and tells them the story about Jack Sparrow which is what he told Will Turner in Curse of the Black Pearl while Jack tries to find the Fountain of Youth.
As part of a running gag within the film, during the Brethren Court scene, Pintel notices that the Nine-Pieces-of-Eight are in fact "just pieces of junk." Gibbs then explains that when the original court decided to imprison Calypso, they were all flat broke. When Pintel then suggest changing the name, Gibbs sarcastically retorts "What? To the nine-pieces-of-whatever-we-happen-to-have-in-our-pockets-at-the-time" and says it sounded real "piratey", referencing the lack of pirate creativity or actual wealth.
Ending up in London, Gibbs is arrested and is wrongly accused as Jack Sparrow. The real Jack Sparrow, posing a judge, comes to his friend's aid and gives him a life sentence instead of the expected death penalty so to get answers about the impostor posing as Jack to gather a crew. After being arrested by the royal guard, Gibbs managed to steal Jack's map and memorize it, possible from photographic memory or something, prior to burning it so that Barbossa would have no choice but to take him along to search for the Fountain of Youth. Eventually reunited with Jack, Gibbs uses his captain's compass during the climactic battle to find the Queen Anne's Revenge and get the bottled Black Pearl, stealing the rest of Blackbeard's trophies of war and treasure in the process.