Hmm...
In terms of the "clever protagonist" aspect, I would recommend Trash of the Count's Family. The main character in that one has a similar attitude to this one when negotiating with enemies and likes to bluff. Though there isn't much large-scale war yet in Trash of the Count's Family.
For the kingdom building and war aspect, I can recommend Rebuilding of a Nation by a Realist Hero, Strongest Dull Prince's Secret Battle for the Throne, Moonled Journey Across Another World, and The Girl Raised by the Death God.
The first two could also apply to the "clever protagonist" aspect. They have similar attitudes to this main character, except they don't have a particular weakness for a girl, and instead just decide to help for their benefit or their family's.
I'm really interested in the rebuilding of a nation but I think it isn't here so can you tell me where to read it?
The title for it on here is Genjitsushugisha no Oukokukaizouki. The novel is getting an anime adaptation sometime next season or the season after, so there's something to look forward to as well.
Also if you want a somewhat more mature/darker version of Realist Hero, there's The Legendary Rebuilding of the World by a Realist Demon King.
In Realist Demon King, the main character is transmigrated into the body of a Demon King from a video game he played and is doing some kingdom-building type things so that he can survive when the hero comes to attack the demons like in the game. Realist Demon King has much more scheming (the author likes to trick the readers too sometimes) and bluffing than Realist Hero. In Realist Hero the main character still needs to appear like a hero and have a decent reputation, but the main character of Realist Demon King doesn't need to worry about that. Also, just wanted to clarify, Realist Hero and Realist Demon King are completely separate, they just have really similar titles lol.
I WANT SOME RECS THAT IS LIKE THIS PLEASE !!!!! ε=ε=(ノ≧∇≦)ノ