I'm working on Lost City, for a Dragon Longsword. 
Need to get my crafting up though. 
So you're a member now? gratz.
Other quests I recommend:
-Monkey madness, for dragon scimmy
-Priest in peril, to access morytania
-Ghosts Ahoy, for the ectophial
-Plague city series, for access to west ardogue, the elves forest, the underground pass, and more
-The Dorgushaan Goblins series, to access their capital city underground, as well as their agility course, a shortcut to the kalphite cave, and a totally cool cross bow capible of hitting up to 600 in optimal conditions.
-Roving Elves, for the Crystal bow and shield
-Temple at Seniesten (and its massive list of reqs) for ancient curses
-Desert Treasure, for ancient magiks
-Lunar diplomacy, for lunar magics
-Dream mentor, for more lunar magics
-Shilo village to access shilo
-Tai Bwo Wannai trio, to use the village to the max, as well as to use the altar there
-Fairy tale part2/3, to use the fairy rings, and eventually without needing the staff
-Garden of tranquility, for the funniest quest in the game
-Nature spirit to access the swamp in morytania
-Myreque series to access burg de rot's bank, the temple trecking/burge de rott Ramble minigame, Meirditch, and the paterdomus catacombs
Of course, those will take a long time, but are good quests to strive for eventually.
Other fun things to do:
-Play castle wars
-Play Pest control
-Play soul wars
-Play more castle wars
