Lost City - This allows you to OSRS gold wield Dragon Long or DDS. Monkey Madness – Allows you to wield D-Scimmy. Heroes Quest – Allows you to wield D-Battleaxe and D-Mace. Tears of Guthix: Allows for free EXP in the lowest level of skill (non-Cbt) every 7 days. Lunar Diplomacy - Allows You to begin using Lunar Magicks. Fremmenik Trials- Permits you to wear Fremmenik Heads (archer, farseer and warrior) Fremmenik Islands ( Requires F–Trials ) This permits you to wear the helm of Neitiznot, with good str & prayers as a bonus.
Probobly 90% of these listed above will not be accesable to you as soon as you become a member. You will have to complete other smaller quests and gain levels of members' skills before you can start many of buy RuneScape Mobile gold these. Although I wouldn't suggest setting a goal to achieve all of these, I do believe they are worthwhile long-term quests.