I havent played this game for awhile but wat new stuf can you experience if you dont buy the expansion? Thanks

No you do not need an expansion because Guild wars and Guild wars factions are stand alone games.

Factions is like a Stand Alone expansion. It can be played without Prophecies but when merged will add more content to the original game.

Well if you refuse to buy it and you already did much of GW then you wont have any new experiences unless you never tried Sorrows Furnace, UW, Fissure of WoE, HoH.

But there a re titles now, you get them by doinbg certain stuff like exploring Tyria, Completing every mission with bonus, opening chests, identifying rare items(must be gold), getting drunnk in-game, etc.

There IS a stickied FAQ to read, this is possibly the most frequently asked question.

GW:F is a stand alone game, original is not required.
GW:P is a stand alone game, expansion is not required.