jewels and set ????

Hello friends, could you help me? I have several in-game jewels that I haven't leveled up yet to use them more effectively. I currently play as a Ninja, but I don't know which equipment works best and which jewels to enhance to improve my level 100 Ninja character.

Also, I have a level 80 Blade Master that I try to use in the arena, but it hasn't been very successful. Which jewels and equipment should I use for him? I hope you can help me. Thank you!