Or gate the loot by game time or level.
Riot's solution to Kleptomancy was poor, because even with lower drop chances, people can still get lucky enough to proc Klepto twice and loot bags of gold with 110g in them. 110g is like what, 4 minions? 3+cannon?
Now imagine if people couldn´t get 110g gold bags until they were level 13? Or say, 30 minutes in?
Heck, imagine if the max amount of gold you could get from the bags was 50 and they couldn´t be sold anymore?
Nerfing Klepto's drop chances doesn´t solve the issue.
However, putting its RNG under control does. Lock items out, reduce elixir of skill drop to a bare minimum, make every potion/elixir drops have 1/4 of the potency. They´re already powerful enough on their own. The fact they get essentially 20% more powerful due to the rune tree combinations makes nerfing their potency no less than absolutely deserved.
Gold bags can´t be sold anymore, and can give anywhere from 0 to a maximum of 50 gold. There has to be a drawback to getting Klepto procs. Some actual risk to dedicating mana to proc it.
Klepto's problem isn´t it not having a cooldown, it´s rather the RNG itself giving champions extremely valuable resources that negate their weaknesses. GP's weaknesses are having no actual power until Triforce, having to manage his mana and deciding between poke and farming with Q and/or barrels. Now with Klepto, his Triforce powerspike comes earlier, his mana issues are gone because C. Pot and the mana pot loot have their potency increased, allowing for both poke and farming with q and/or barrels instead of having to pick.
Current Klepto is nerfed in the wrong way and despite the Inspiration's tree thing being about bending rules, Klepto even in its current state not only bends rules, but breaks most of them entirely.
would propably still like it, but he won't get a ton more value out of it than 
for example.
