When your at lvl 55 with your gear on you want your dex to be around 110-120. Put the rest of the stats into strength
If you would like to know what items to look for here they are.
For items-
Weapon- Enhanced Effect( the higher the better)
Armor- For catacombs look for heavy armors with EE. For arena look for heavy armors with stats such as strength or dex
For charms- Look for stats such as strength or dex