Restrict. Klepto. to. melees.
I was indifferent to Klepto no more than 1 game ago where I had the honors of facing a top lane Kennen with it. You may say a single game couldn't possibly justify restricting it, but let me tell you otherwise. My point will fixate on the core issue with Klepto rather than the gold value that its users get out of it.
That point is that Klepto gives gold for hitting. I don't care that Klepto is free gold. I have no problem with that since it comes at the expense of an actual keystone. The problem arises when you're scared of even trading into your enemy laner. It promotes the most one sided interaction possible.
Being the top lane Ekko main that I am, I've always been willing and able to trade into ranged tops, but when I checked his Klepto at 12 mins it read 455(!!) gold + 5 items. That's 1.5 kills and at least 100 more gold on top of it. The Kennen could've realistically been a whole item or half an item above me if continued trading against him. The solution? Roll over like a good boy and don't even attempt to fight.