Reccomend me some armour and weapons for an Ornstein build?

You are missing the Spear though.

No Armour looks anything like his.

Could I use a lightning staff for weapon?

It's your build so it's your choice.

I think a Lightning Staff with an Iron or Steel Sword would be ok. Hou could do the Staff glitch so you have a melee staff. Takes up a about 30-50 carry weight though.

I'd say you'd be better off with a Smough or maybe even artorias. But not Ornstein.