For the trivia you could include questions like,
Which item/items are required to kill Cave horrors,
What attack level is needed to equip a whip
Where is Lowe Located.
There Is such a wide range of questions that you could add some easy, Medium and harder ones.
Some more simple questions, I noticed quite a few people needed people to tell them the answer to previous ones like Max level, Hardest mob Etc I'm willing to write a list of different Ideas If you want but would rather give others the chance.
As for the forums I would like to see a type of Question of the day, And more interactive posts like the Goals. Another one that could be popular is a Log section either Pvm/Slayer kill/Loot logs, Personally I like to read and look at other peoples achievements and drops.