I can help you on that.
The level that a weapon can get with Peridot is based on your character level and highest floor you have been.
If highest floor you have been is floor 60,and if you are lvl 60,then the equipment level can be lvl 60.
But here's the catch.The max level the equipment can get is character level*2,with equipment level cap being 100.
So if you reached Floor 1000,and currently lvl 34,you can upgrade your equipment up to lvl 68.In order to have max level on all equipment,you just need to be lvl 50 and the highest floor you have been should be 100 or more.