Basically you need at least 3 roles in order to reach higher levels of endless tower. But It will be more efficient if you have 4 roles in the team.
TankThe tank serves as absorber of damages for the team. He is usually at the front being flocked by mobs so that the team will not be targeted. He plays an important role during MVP rooms because he will be absorbing the damages and keeps the MVP away for the team. Best class for the role are Sura in Mental Strength state. Next would be swordsman classes. Other options will be any class as long as they have Devotion from a Royal Guard
MVP killerThe MVP killer is a key role because he is responsible in killing the MVP Boss monsters on green rooms. He will see to it that he will be able to take down the MVP as fast as possible. Best class for the role are Genetics. They can dish out almost all MVPs except for ghost property. During Endless Tower run the MVP killer might vary depending on the MVP being faced. Best class for killing Ghost MVPs would be Lord Knight under Gloomy Shyness buff with elemental weapon or converter. Other options will be Sura.
Mob ControlThe mob control is responsible on killing mobs during normal rooms. Sometimes they are responsible in clearing MVP mobs so that the MVP killer will have a clear shot on the MVP. Basically this is any class with area attacks. Best class for the for the role are Warlocks, Sorcerer and Rune Knights.
SupportThe support role is a role that can be sacrificed out of the team during Endless Tower runs. However the run will be easier and fast pace if you have supports on the team. Basically its a role that will make another member more efficient. More supports means better performance. Best class for the role are Archbishops and Minstrels.
General Gears to wear:
Team members will be able to survive the dungeon with Hodremlin Carded Shield and tanker with an extra Alice carded shield during MVP rooms. Other gears are job class specific depending on the role.
Important Items to bring:
Surviving in the dungeon becomes harder as you go up the floors so it is important to bring HP and SP potions. Do not expect that your Priest class team member will always be there to heal you. Green Pots is also important to quickly remove status ailments. For Power leveling do not forget to bring Field Manual and Job manual. Neutral Ring for Ifrit room is optional.
Hypermart consumables will also help especially Token of Ziegfried. It is the only item that ensures second life when the team is wiped out. Priest Classes and Wanderer/Minstrel are encouraged to carry a token of ziegfried since they have a skill to resurrect other team mates. Insurance is also important when you have experience points to burn. It will hurt your travel if you burn more experience points more than you gain.
One hour Food Buffs are optional items to boost stats. It's a good replacement for Archbishop buffs but of coarse having both buffs would be better. Geffen Scrolls is also a good addition. Both One hour Food Buffs and Geffen Scrolls persists even death so you will enjoy the benefit for the whole duration of the buff.
How to Jump:
Jump is a term used in pRO which refers to skipping floors in Endless Tower. Skipping some floors is a good way to bypass low level floors especially if you aim for power leveling until Ifrit room.
To start the jump you need to have the item called Ashes of Darkness. At the first room locate the Immortal Brazier at the base of the room. It is the first torch that you will see once you enter the Endless Tower from Misty Island.
Talk to the Immortal Brazier and it'll give you three options to jump. But each option will consume Ashes of Darkness depending on how far you want to jump. The 26th floor jump requires 1 Ash, 51st floor jump requires 2 Ashes and 76th floor requires 3 Ashes. If you aim for Ifrit 51st or 76th floor is advisable.
An Ash of Darkness is given everytime you clear the 25th, 50th, 75th and 100th floor. So if you finish the Endless Tower from 1st floor to 100th floor you will have 4 Ashes.
How to use Purification Stone:
Purification Stone is a Hypermart Item that lets you bypass the cooldown set on an instance dungeon.
For Endless Tower once you got out of the tower regardless of reason the team member will have 1 week cool down to re-enter the Endless Tower. In order to bypass your cool down, purchase a Purification stone at the nearest Valkyrie NPC Hypermart.
Locate the Underworld Admission at the other edge of Misty Island.
Talk to the NPC and give the purification Stone.
Congratulations you may now re-enter the dungeon.
Credits:Special thanks to my friends whose names appeared on the screenshot. Your talent during the photo shoot is outstanding.