this Post gives some great information on the basics of making a Build that can do well in Battle Arena. it also explains why certain affixes are used. the rest of the Build can be just like shown or changed to a Build of your own design.
the +100% Shock DMG on your MH could be taken out and replace with +5000 WD or something else. or put +7500 MP on your MH & take the 7500 MP off of your Amulet and put a +5000 Shock there instead.
the Set on the Pet is Terrashaper, but I don’t remember the name of the Pet.
I am also not very good in Battle Arena, so don’t forget to do a Search in case there is information in the Forum that the rest of us don’t know yet.