How many Alloy Foundries you need

[Dubadam]

they all end up being overwhelming fleet power

That's because they always try to have their fleet size close to the cap. And if you still have those 3 free corvettes it's inevitable that their relative fleet strength is "overwhelming".

Just pump up your fleet size and you'll quickly become even with them.

Well, if your neighbor is not a devouring swarm I mean.

 

[AGenericAccount]

In current version, it's best to specialize your economy.

During time of peace/ when you feel safe, from nap/ defensive pacts, you should enable civilian economy/consumer trading, replace all your alloys with civilian industries/labs,

During war/ when you don't feel safe, you swap to wealth trading, militarized economy, and alloys.

The 10 year truce from breaking nap is a great time to start changing your economy from civilian to war

At start of the game, when you don't know your neighbors, it's best to go military economy, 4-5 alloys and stockpile them because you can't feel safe if you dont know who your neighbors are. You should only swap to research only when you know that your safe and have a decent alloy stockpile.

Alloys first also have the benefit of settling border disputes through war

I feel like this is a really bad idea, considering that you have a net LOSS when you decide to specialize CG or alloys. Just keep the economy the way it is and you can buy/sell on the magical galactic market. Economically, it makes more sense because the market rates can't be worse than the reduced production that specialized economic policy brings.