Expert Businessman, if memory serves, primarily works on investments.
Which would mean the best way to leverage it is to invest in all the carvans, islam up to the cap it allows you, catholics up to the cap it allows (if atheist, you can push both to like 70 I believe), Aimee's shop, Ansel's friend's shop, the bar, And the two Redhaven shops. Also, establish the news station. Get Rebecca set up as your skullduggerist to compound with the businessman bonus. If you're willing to keep your prayers up, you can just go Islam to get another boost to your passive income types.
The Entrepreneur bonus from Expert Businessman works the same as your accountant's bonus except it's much smaller. It can still ramp up to where it's significant if your faction income is really high, but the real bonus is the 10% boost to workshop production. That's what you use to pump up those factions (primarily Aesir, Fort Sera, House Carossa, and the Underworld).
The bonus for Islam sounds good in theory but they're much harder to boost to relevant levels than Aesir is. You can pretty easily pump Aesir up to where it's giving you several thousand dollars a day by itself. The Catholic Church can eventually be good but it takes a lot longer to ramp up. You need a combination of high crafting skill to make gold necklaces to donate to them, plus perfectly trained scavengers with the scavenger trait to generate merch, plus both farms and Burakumin village maxed out to produce a massive food surplus. You can do that eventually but it's not possible in the early to mid game. It's a late game option though.
Aesir you can get as a full vassal in less than a month and can pump it up to 3000 or more income in 2 or 3 months. Same with Fort Sera. The bandits can be good eventually but they take a huge investment to get them to 100 standing and they give you absolutely nothing until that point so they're not a good choice to dump your workshop production into initially.
Early game I would focus on the higher ROI investments like Aimees, the Orphanage, your first workshop, Roos, Waltons, and the Wrool Cat Wranglers. Completing Caitlyn's quest is also a good early option since it's pretty cheap to max out her Clinic when you finish her quest and it provides good income.
If you have some NPCs who are close, but not quite at the science threshold to be a full professor it could be worth your time to home school their science enough for them to be full science professors.
If you build affection with your mercs to loving or better, most of them can be convinced to sign slave contracts reducing their salary to $0.
If prosperity is low, one of the best investments you can make is to complete Averil's quest as soon as possible because then your food costs permanently drop to zero and you can ramp the farm up to enough food production that donations to the orphanage will raise prosperity and thus eliminate that prosperity mod penalty (which can be huge since it's essentially like a negative accountant bonus). It's also a great way to enable ammo pack on most of the people who have that trait. Clea and Bud are the only people with ammo pack who can actually use it at less than 10 prosperity.
