Interesting thread. I tried it out with an Aksum-Xerxes (Achaemenid)-Archipelago game. This configuration justifies a game focused on gold income as I wanted. Gold adds a lot of versatility to the strategy, and I think it's a good option when the game setup or circumstances make boosting gold more effective than production, culture, or science. I used the 1-cap Memento for settlements to alleviate the drawbacks of not having the settlement limit extended by other means (with the current 1.2.1 patch). With the help of about five promoted Dhows, I was able to conquer two more settlements, plus two more through peace treaties. This secured the 3 military legacy points, which, as mentioned by others, are important for extending the settlement limit by 2 in the Age of Exploration.
I think something that should be discussed and I haven't seen in the posts in this thread is civilization attributes. Thanks to Lord Yanaeka's thread in the Strategy subforum, you can learn that attribute points aren't random (at least largely). So this can be planned and adds dimension to the game. In this case, Aksum is both economic and cultural, meaning you'll get one cultural attribute point for researching six Civics and one economic attribute point when you have two trade routes. A third attribute point (to choose between cultural and economic) is earned by completing the Aksum-specific culture tree. So, in my gold-focused strategy, I used the economic attribute Memento and then Askum gave me two more rather easy. Also, since I went to Navigation relatively early to promote Dhows, I was able to get the Colossus (which gives an additional economic point). Xerxes activates an attribute point when researching Code of Laws, which, it seems, will be one of his two attributes (also economic and cultural in this case). It's a bit obscure how to get the one you want, but I was asked between two monuments and two altars and, effectively, excluding the first one for cultural reasons and after the second request, which I don't remember, but was easy, I ended up with one more economic attribute.
For the Age of Exploration, I'm going with Chola and three additional economic attribute points (Memento plus two economic points from legacy points). With this, I've almost finished the attribute tree at the start of the Age of Exploration, and I think that as soon as I get an alliance and a little more, I'll have about 1000 gold per turn.