State, 0% autonomy, convert to own culture and religion with religious culture privilege, 10 dip
The problem with stating gold producing provinces is that none of the provinces in that state can be in a trade company. So you get reduced trade power (which can be significant if any of the provinces contain an estuary and/or centre of trade and/or if that state contains many provinces which could otherwise benefit from trade company buildings, especially if that's going to help you to get 50% province trade power in that TC region to get an extra merchant), also it means your institutions can "leak" to neighbouring less developed countries (making future conquest more difficult), though this is reduced if they have bad relations with you.
Also, what do you do with the remaining provinces in that state? If you leave them as territories, you're mostly not going to get much income from them, but if you full state them, then that will cost you more MP and governing capacity, though they will be easier to convert to your religion (and therefore culture, once separatism has gone, though that will cost a few more MP too and takes a lot of time).
So I think it's a bit situational whether you state a gold-producing province or not and whether to develop them or not also depends a bit on what dev cost reduction modifiers you have.
One African area I do often full state are the provinces in South Africa, at least a bit later in the game, once you have plenty of merchants anyway, as some of the provinces don't need to be converted to your religion if you've colonised them yourself (especially if you kill the natives first and most provinces there don't have that many) also there are not many neighbouring countries to leak your institutions to - usually just Kilwa, which will probably have bad relations with you.
