How does Dorian Gray's outlook on the world change throughout the novel?

Dorian Gray's view of the world changes dramatically as the novel progresses. At first, he is pleased to sell his soul, in order that all of his sins and signs of aging show up on his portrait, while his own body remains young and unblemished. He indulges himself freely in decadence, believing he won't have to pay a price for it. This seems a good bargain to him.
As time goes by, however, Dorian begins to see the limitations in a life of hedonism. The trade off he has made no longer seems so good. He increasingly doesn't want to face who he is and what he has done. His body might not show his dissipation, but his actions weigh on his memory. Wanting to forget, he tries to throw himself ever more into the sensual world, to barricade himself in it. He wonders,

"To cure the soul by means of the senses, and the senses by means of the soul!" How the words rang in his ears! His soul, certainly, was sick to death. Was it true that the senses could cure it?

By the end of the novel, however, he is sickened by his life and by the horrible monster he sees in the portrait of himself. He no longer wants to face that person: the real him. He learns his deal with the devil has been an error. He stabs the portrait but because it is him, he dies, taking on its grotesque form, while the picture converts back to the young Dorian.

At the start of the novel, Wilde presents Dorian Gray to the reader as an extraordinary-looking and impressionable young man. At the start, Basil, an artist, makes a fuss over Dorian, unworried about the effect such attentions might have on him because Dorian is not at all spoiled by his beauty. Dorian's outlook on the world is still innocent. It is only when Lord Henry meets Dorian and speaks with him frankly about the value of beauty in the world of pleasure-seeking Lord Henry inhabits that things change.
Dorian begins to transform into an amoral hedonist only after he learns that he has power thanks to his beauty and youth. At this point, his outlook on the world becomes a self-centered one, and he looks at individuals he meets as objects to be used for his own entertainment and enjoyment.

Throughout the novel, Dorian Gray's outlook on the world changes fairly drastically.  At the beginning of the story, Dorian is young and easily influenced.  He is beautiful, which makes him the perfect subject of a portrait by artist Basil.  Basil uses Dorian as a muse, and introduces him to Lord Henry.  Under Lord Henry's influence, Dorian learns that he can get away with a lot because of his beauty, and he also begins to feel that life is meant to be lived by taking what you want.  
This hedonistic world view causes Dorian to make a declaration that he would sell his soul to stay young and beautiful forever.  Dorian later learns that his fate has been tied to Basil's portrait of Dorian, leaving Dorian free to explore a world of excess and pleasure with no physical repercussions.   Dorian, throughout the rest of the novel, becomes increasingly hedonistic and arrogant, and he is constantly finding new ways to entertain himself.  He believes that the world owes him constant entertainment.