Try Haku, Kisame, and maybe Gnw Tenten/Chojuro, they're all good for dmg, as for summon, try tonton, and for skills, sharkbomb/skewering, whip/strength, water trumpet, water boost, and water clone. Give that a shot, if you want, I tend to have it like this.

Haku X X
Kisame Main MainClone
Chojuro X X

Chojuro can be replaced with Tenten

Well, no, I'm in one of the older servers, and I'm not the strongest. Most people I see use a lightning or a wind one. But hey, see what the others have, I just put a basic one I thought would be good, I didn't just throw together random people.