From pottermoreanalysis:
Gryffindor
Gryffindors are another individualistic House, but one that's primarily defined by its daring, desire for fame, and great exploits. (Some parts of the quiz are less useful for defining Gryffindor because of the quiz's overall bias towards this House: in many cases, the answers that give points to Gryffindor are chosen by everyone and therefore not really useful for defining what a Gryffindor is. Per JKR, Gryffs have more of an interest in ghosts and cure>book>records - but the numbers aren't working out that way. Per JKR, Gryffs want to be trusted and praised - but so do Ravenclaws, and in greater numbers than the Gryffs!)
But what the quiz does say about Gryffindor: they're fiery, and defined by a desire for glory. They want to be remembered for great adventures, and are the most likely to leap before they look. They're the first to charge into a situation, the first to defend their friends. They prefer to deal with a situation directly, even if it means a fight - and they want that fight to be a fair one. They care enough about justice to get into a fight, even if that fight involves an argument with a friend.
Gryffs are deeply, deeply defined by forests, and by the element of fire. Fire here is actual fire: not Hufflepuff's nurturing sunlight, but an absolutely scorching-hot flame. Fire is passion, and Gryffindors are passionate about their beliefs, and standing up for what they believe in (and, more pointedly, who they believe in: Gryffindor is an individualistic House, but it cares deeply about people - it's not cerebral in the way of Ravenclaw or Slytherin.) A Gryffindor's first impulse is always to draw their wand and act.
Gryffindors also like being around people. They're not group-focused - it's individual glory they're seeking after all - but they like being around friends, and hate being bored. (They may feel the need to make a little mischief to keep from being bored.) A Gryffindor never has to worry about being overlooked - they need to keep friends around them and are a more extroverted House on the whole, but they're generally too active to be ignored. Physical discomfort doesn't bother them at all.
Gryffindors are fully willing to bluff, but never to cheat or threaten (and the Pottermore quiz tends to downplay any and all of the malicious/thoughtless actions we've seen from Gryffs, like James's bullying, Sirius's prank, the twins' locking Montague in the Vanishing Cabinet, Hermione hexing the DA parchment, Harry's interest in an unknown jinx - Gryffs may be interested in pranks and hexing Slytherins in the books, but the quiz completely disregards this aspect of their collective personality - per Pottermore, Slytherins are the only ones ever associated with jinxing people. Not a decision I agree with, but this analysis is based on what the quiz can tell us about the Houses.)
Forests, in the Pottermore quiz, represent both individuality and also danger, to a certain extent: dangerous things are found in the Forbidden Forest, after all, and dangerous things attract Gryffindors most of all. (Not necessarily Dark things - not all dangerous things are Dark. But Gryffindors will go for things that are associated with the forest and have a reputation for danger. They're also most strongly associated with ghosts, although that's not particularly an association I agree with or have a good way of working into this analysis.) But forests and fire are Gryffindor's defining elements on this quiz, and forests + fire + action = a very Gryffindor individual.
Gryffs do care about people, and seek external validation from others: they're very interested in proving themselves. A Gryffindor is going to be very interested in being a hero; as Hermione has said, they may have a "saving-people-thing." They don't care about knowledge as much as Ravenclaws, and certainly aren't interested in knowledge for knowledge's sake: if they want to save something, it's going to be something that enables them to help others, and if they want to learn something, it's going to be something that allows them to pursue adventures - ways to get about undetected, for example. They do dislike things that they consider boring and/or useless, and would prefer to seek the unknown rather than treading the usual paths - but less out of a desire for intellectual discovery and much more because of a thirst for adventure. Adventure, and more importantly action, are the traits of a Gryffindor: Gryffs want to be heroes. A willingness to confront the darkness, to fight for the underdog, to explore and defend: this is Gryffindor House.
YOU ARE READING
Harry Potter Theories/Randomness/Memes
FanficMy Harry Potter Theories. Feel free to comment yours! Also this contains my attempts of the actors texting and some randomness.