Hi there tuckab!
It all depends on where you want to see progress, but normally i would suggest Sigmarus after Vero. He will do you well in DB10 and ToA due to his CC. Panda is good for Necro or Raid, but in my opinion that should not yet be your first priority.
Though if you have Chloe you could consider Katarina, they work quite well together with Chloe’s invincible skill and Katarina’s 3rd skill that ignores defense in invincible state.
Hope this might be enlightening for you 😀