A bit hard to answer concretely, since it depends on what opener you use.
But generally speaking you want to settle over developing your lands early on.
Getting builders increases the cost for future builders (which is why you want to wait for serfdom), and districts generally dont pay off to build early on unless its holy sites, commercial hubs or government plaza.
You keep district costs low by locking in the cost if you dont intend to build them right away (just placing the districts and not building them), and you can keep the cost down further if you skip turn rather than finish up a tech (only works on pc afaik).
That being said, there is the religious opener where you generally can do both, so it doesnt become a tradeoff, but it depends on map RNG.
The religious opener heavily uses adjacency pantheons, rushing a religion off of 2 (max 3) cities, and frontloading huge production from work ethic.
The production you get from good holy sites outweighs any production you would get from increasing population and improved tiles early on, and it fuels a faith based economy.
If you can pair that with monumentality golden age, you can generally chain purchase settlers early on, and use those to settle even more lands where you can leverage your faith pantheon, build more holy sites for more production and faith, and essentially just snowball yourself to victory.
You want to pair 4x Moksha as the governor of choice in that case, because that allows you to instabuy districts, which means that you can create a self sustaining snowball where you faith purchase a settler, settle some high faith lands, buy the holy site with Moksha, and buy even more settlers.
Pair it with government plaza and you get a billion free builders from it as well if you chose the Ancestral Hall.
The other way to play is to rush commercial hubs in all cities, and in that case you can argue for Magnus and a few builders to chop out the commercial hubs.
You want those for trade routes that frontload food/production for you.
I would stay away from spamming campuses early on, thats usually a mistake that people do on lower difficulties as it doesnt help you set up a snowball, and will only put you further behind long term.
People generally assume that you need to spam campuses "because the AI is ahead", but thats the wrong approach, as they will be ahead regardless of what you do, and thus its better to voluntarily stay behind a bit to mass settle and set up strong infrastructure (holy sites or commercial hubs), and only then start explode in science/culture in the mid game when you have already set up the necessary infrastructure.
