https://forums.civfanatics.com/threads/balancing-city-state-rewards-tribute.656394/
Prior Thread. Has these suggestions, mostly.
One key is that the yields from city-states aren't really balanced. Maritime city-states food are nowhere near worth tributing for food. Culture and faith aren't really worth it much. Production has a niche use sometimes but also drops off. The Culture from tribute policy also isn't worth it, and balances against Heavy Tribute with the percentage system since you get less tribute than just gold. Maybe the base of that should be double culture from heavy tribute, so it would be about the same culture if you take gold, or take heavy tribute.
Another key issue is that quests are an extremely valuable aspect of city-states, and tributing for weak yields, causes you to miss out on them. So like I suggested, Tribute social policy allowing bullied city-states to still give quests would redress the balance somewhat. The influence gain wouldn't do much since you start below zero. But the yields are helpful, and sometimes in the early game, the only mass source of stuff like golden age points.
Another thing that is a issue, is how Tribute only boosts the capital, not other cities. When Authority is usually wide. Maybe a way for Tribute to go to other cities.
Bullying for resources as an option would be good.
I suggested that yields would evolve so, in later era, you can obtain GPP.
But overall, Tribute would really be better shown as Tributary relationship, which would be like an ally status, but one that only lasts as long as the city-state is scared of you. Not sure if that is possible to code, but it would better represent how minor powers interacted with empires. Being able to be a diplomatic power should involve having some power to back you, not just spamming diplomats.