here are some simple tips for fb39. First and foremost, tab holder must have the 3 tabs and be sure that you have enough space in your inventory.if you are  interested in it .just look through.Hopefully the article can help you. I believe you will learn something from it.

Classes that needs to be in fb39 squad:
lvl44+ barb w/ 3k+ hp = The barb will serve as a TANK, he / she will take all the hits and must take agro always.

1/2 lvl40+ cleric w/ iron heart blessing [and Party heal if possible] = Clerics will serve as the life saver of the squad, Its a must for them to retain the TANK's hp in full and if a barb/bm[tank] is about to tank a mob / boss,start putting/stacking up iron heart blessing.

Veno lvl40+ w/ lvl40+ pet = Veno's will serve as lurer's, they must lure mobs 1 by 1 and be sure that your pet wont die when luring or else the mob's around the mob that youtried luring will come and take your squad down.

lvl45+ wiz w/ 1.1k+ hp = The wizards will serve as DD and they can also TANK the last boss because of their uber mdef [Last boss is a magical attacker] .

And of course the tab holder, Tab holder will support the team [unless your a barb/tank], just dont die.

A lvl52+ BM w/ 2.2k+ hp could also serve as a TANK or a Sub tank, use your stronges skills so the mob/boss will focus on you/bm.

MOBS:
In the dungeun, their are mobs that explodes[Reverex and the chicken], in this case, the tank must take agro of it and keep the mob away from the other squad members. If 2 exploding mobs come, tell one of your squad member to try luring/taking agro of it out of the squad's area, hit it and run[like playing tag],wait till one of the mob dies and bring it back to the tank/barb.

Their are also mobs that uses AoE [The ghost lady on the last boss], and for this scenario, Tankers must not get too near to other squad members. If 2 AoE mobs come, Cleric should use its Party heal, and one of the squad member will hit it and run[like playing tag again], and wait till one of the AoE mob dies and bring it back to the tank/barb.

Their are some runner mobs inside the dungeun, veno's must lure this mobs 1st. Clear up all the runners before you start proceeding to the next place/room. Most of the fb39 squad dies because of leaving the runner mobs behind. Have patience, wait till the runner mob comes closer and thats the time to lure and kill it.

And last on the line, the mobs around the boss [its minions], veno's must lure boss's minions 1 by 1, if your pet die, tell it to the squad asap, cause all of the boss's minions including the boss will come, if this happen, dont get panic, tank/barbs will take agro of the boss and run, dont run towards your squad members, instead run opposite to your squad members, other members must take care of the boss's minions, If their are 3/4 minions came, Veno must take one and let your pet tank it[revive your pet asap], sub tank/bm [if you dont have a sub tank then the DD] must take 1/2 of it, stun all of it or let it chase you, wait till the veno kill one of the minions and bring it back to him/her, Clerics will support the sub tanks and veno's, once all of the boss's minions die, call the tank/barb to go back and start killing the boss.

Some info's about the 3 boss:

1st boss looks the same w/ its minions so be careful and it uses AoE [25m range], other squad members must try moving away from its 25m range and use your farthest skills.

2nd boss also looks like the same w/ its minions and it is not an exploding boss.

3rd boss is a magical attacker, let the wiz/veno tank it and clerics must focus heal on the wiz.

Lastly, if their are mold drops and 3* star item drops. Dont be selfish, share up the items or if someone needs that item and you have it, sell it to him/her in a lower price. You all help each other to finnish your fb39 quest, so everyone on the squad deserves a credit.