Tips on how to do both world bosses that will spawn at the same time:
A. If you have a dream horse, you can easily do transition from world boss to another with a single character;
B. If you don't have dream horse at the moment, you can create an ALT which is dedicated for doing world boss.
I suggest to go wtih Witch/Wizard/Ranger/Archer class. Level it up to 56 or higher.
I suggest gearing it up with grunil set, DUO is good, TRI is better. And blue grade accessories duo or tri may do.
As long as it have a decent DP and AP you are good to go with a higher chance on getting that precious items.