http://irowiki.org/w..._Dungeon_Quests
Before you say "It's VIP only, the reward for completing all the bounty boards is a card of you'r choice, some with values of 15m!
When you hit level 30 buy 2x Magic/Reset stones.
This will cost around 10m, reset assure you will make this back!
Head to Gramps inside Edens and ask for the "3day VIP package"
Entrance to Overlook Water Dungeon.
You can get access without VIP for 2x reset/magic stones, but it's best to get VIP through gramps as you will gain additional benefits such as VIP buffs and summoner.
Each floor has Bounty Boards which can only be completed once.
The exp reward is VERY HIGH and when you have completed each and every floor you will be giving a free card. Marc or Phen are you best options as both have good market values in which will refund you're reset stone investment.
At level 30 you may have trouble hitting monsters so a quad mummy card is good, a wind endow great and fishing % even better.