It seems there is some evidence for cherries lowering UA. But we’re probably talking about a whole lot of cherries on a daily basis if you want to get a significant effect out of that… at which point I would be concerned about cost and possibly side-effects.
There is apparently also evidence for milk and yoghurt being useful. If you’re not allergic to this stuff or something and don’t overdo it, the worst case scenario as long as you also pursue proper treatment would be that you’ve treated yourself to a placebo.
The least harmful thing you can do I think is to make sure you drink a lot of water (within reason) as well as to follow reasonable and generally-accepted dietary recommendations such as favoring a variety of vegetables over hamburgers.
I’ve been told that UA can unusually high as well as unusually low during an attack. In any case, there are other confounding factors and some data is better than no data. But I guess waiting before a test would make sense if you can only afford one.
And in answer to your earlier questions, slow buildup is possible. In particular, it seems flares can get worse as they move between different parts of the joint (or to the joint proper from a connected part – I’m terrible at anatomy) if you count that as buildup.
I found general-purpose anti-inflammatories have a way of dialing the symptoms way down without getting rid of them entierly at which point it becomes easy to have anything misdiagnosed as a routine one-off problem.
In any case, I can’t diagnose myself so I wouldn’t even dream about diagnosing you remotely.