I tried a character who was Attractive-Sharpshooter-Artisan which I combined with Dominant-Frightening just to see how it would go. Intelligence started low, but I found if your INT is that low there's more chances to increase it, something you never find out if you always go Brainy-Gambler. Within a few hundred days, maybe a year, I had INT up to 60 through various increases playing cards, playing games with Ansel and sometimes just for waking up in the morning.
I suspect if you want the best benefit in the very longest term it's arguable that starting INT doesn't matter as much due to the above. In the middle term that INT allows you to get the courses and books done at more optimal INT values quicker, but the opportunity cost might be having to craft hundreds more combat knives to get Blacksmithing and Artisan up etc.
		
		
	 
Yeah I've tried similar builds where I started at low int, whether it was a rise from the ashes start or just a start where I intentionally did not take brainy or gambler.  IMO, grinding int up is harder than grinding anything else up though.  So the ashes start is really the only case I can see where I would not take both Brainy and Gambler.
In my current game I focused on getting a bunch of slaves asap so I could get started on training up discipline with my head maid and my slave mistress and then build a workshop on day 22 before I had any other upgrades except the healing implant.  By day 25 I had the workshop fully upgraded plus the first tools upgrade so I could either have it generate $500-600 a day as a sweatshop or crank out rifles to sell or donate.  That's roughly the equivalent of the investment in Roos before it's possible to make that investment and without being degraded by the dockpunks (which you can't wipe out that soon).  The last 2 tools upgrades are really expensive so I plan on doing some other upgrades before those.  The workshop also makes completing the Belial Guns quest trivial without needing any crafting skill and without buying anything.
Since I went with Brainy/Gambler/Nerd I can do Aisha's quest as soon as I hit 10k influence without needing any academy classes or books so if I want to I can grind my int up as high as I want before I start doing classes or books.  Mai Lynn's hacking quest requires 100ish science but you can just bypass that requirement by buying the seeds if you want.  Or wait however long you want to actually start her quest since the Toshi Gardens investment is a terrible return on investment.
The new Gazebo upgrade is amazing for progress with the girls.  Even if you take nothing that boosts your initial charm or manipulation the gazebo can quickly boost everyone in your house to 100 happiness and decent affection with zero chance of failure.  So sexing up the girls just means building a gazebo and throwing some pool parties before you start working on seduction or request sex.
Manipulate is actually not that tough to boost if you know what to do.  Request sex has a chance to increase it, but the real key is to focus on explain chores and explain sex duties.  Both of those options have a relatively high chance to gain manipulate (by Grim standards, so like 10% rather than 1%).  So you can use that to grind manipulate up past 90 before doing any classes or books that increase it and end up with it well beyond 100 eventually.