Settlements are the best and easiest way to get more followers and belief, because they allow you to build vertically, rather than horizontally. In this case, it doesn’t really matter what kind of settlement you build – it can be a farm, mine or builder’s settlement, or a farm, mine, or builder’s village. Either way, buildings within the immediate circle will all cluster together to form a settlement.
Make it so that each time you build an identical settlement, the original settlement is included in the buildings that merge together, along with whatever abodes are built around it. Doing this will cause buildings to continue moving to the top of your settlement, enabling massive structures, compounds, skyscrapers and other insanely large buildings to be built.
What does this have to do with followers and belief, you might ask? All of the followers from the previous abodes will be grouped into the settlement. All of the breeders will remain breeders, and all of the builders will become farmers or miners, or in the case of the builder’s settlement, will remain builders. All of the plots previously occupied by abodes will be freed up for more construction, allowing more abodes to be constructed.
Keep using settlements to build upwards, and you’ll be able to amass gigantic quantities of followers. Of course, they still continue to collect the belief that they used to. It takes longer to build up enough to become collectable, but you’ll also collect FAR more belief, and the building can hold far higher quantities of belief before it maxes out and requires you to collect from it.
You’ll need to keep your followers happy in order to keep them from straying away from you. This is done by such things as god seeding and unlocking new cards (for that matter, the follower happiness card is unlocked at 245 followers). Also, keep them energized by tapping them and boosting them to keep them happy and to keep them working at full capacity.
When you get into confrontations with other tribes, you’ll be able to convert them to followers. This is done by a mix of defeating them in battle and diplomacy, and when you do this, you’ll open up the opportunity to convert them into becoming your own followers.