Event has better stats, have atk and def. Some better than others. These are worth leveling up
The +10 silver is fine to start with gives 1000 ATK spend your resources leveling event equip first.

I just evolved Kerria's CSQ equipment.
When I look how to upgrade it, I don't see any difference in term of xp amount between the different materials, is that correct?

The Special Equipment Upgrade Material(anvil/chibi-Nazuna) gives bonus xp for character-specific equipment.

Yeah, ten of the gold chibi-Naz materials will get a fresh set of character equipment from level 1 to 44. From there it doesn't take much more to cap character gear at level 50 since you can convert gold earring/ring/bracer/necklace material to Chibi-Naz material at a 1 to 1 rate.

From what I see, a non-evolved CSQ equipment gets the same xp from a gold earring upgrade or a nazuna gold upgrade, but both are higher than rings/necklaces/bracelets.

So it's no use to convert earrings materials in nazuna, at least for the non-evolved items.