The easiest way to solve the problem, as I understand it, is to ignore the urge to cover the whole area in bus lines, because it's expensive and many of them won't have enough ridership to justify the cost. Instead, look where your density is highest, change zoning to let it get even higher, and build, like, 1 or 2 bus lines with very frequent service (less than about 12 minutes gap). That's the magic threshold where you don't need to look at a schedule -- if you miss one bus, a 10-12 minute wait won't make much difference. And that makes it an inflection point for ridership too -- you can get a lot more people with frequent service, meaning you get enough riders to make the whole thing worthwhile.

Best is if you can get a lane dedicated entirely to buses, and ticket cars that drive in it. You want buses to be a pleasant alternative to driving -- since you already have a walk at the beginning and end of your journey which takes time, it's nice if your bus can get priority over car traffic.

And from there, build up the areas with good bus service more and more, add more buses as needed due to population growth, lengthen lines, add new lines gradually as people see the success of the first ones. Incremental implementation is the trick.