I think directing Prosperina to keep an eye on the Marians makes the most sense, followed by the Sullans. The Catilinarians probably won't be making a move unless the Sullans do. I'd prioritize the Marians over the Sullans mostly because they're currently running Rome, a lot of optimates are in hiding after the murders, and we might end up learning what Marius himself is planning, which could help us coordinating our own movements. We're on his side at the moment. If we decide to stage a revolt and join Sulla, then I could be persuaded over to spying on the Sullans, but I still think we'd get more out of the Marians.
I think Theo is the obvious choice here, he speaks Greek fluently, which is a huge boon considering where we're headed. That also means we can pretty safely skip the action to learn Greek for now, as slots are pretty competitive. Carnigaeus is an interesting choice, he sort of replaces Tercerus, but we have one campaign under our belt, we don't have the same relationship with him that we do with Tercerus, and I think we get way more mileage out of Theo. It also lets Carnigaeus stay behind and continue training our household guard.
Picking both Loyalty and The Consul might get us a pretty big in with Scipio Asiaticus, but I'm not sure it'd be worth it. Asiaticus isn't Sertorius, so I don't know how much we'd get out of it other than a possibly new ally, and again, slots are competitive. I think Gather Support is the best option. It lets us stay the most non-committed of the three choices, doesn't have an action that it sort of needs to be fully effective, and ties the legion more closely to us, which is useful regardless of our choices going forward.
The three personal actions are the most interesting choices this update, in my opinion, as far as gameplay goes anyway.
To begin, Si Vis Pacem is a almost a requirement if we don't take Theo with us and is still competitive if we do. Atellus can't give many speeches if no one understands him.
I'll go in order from there. I don't think Writing Home is useful this turn. Cicero can get us Intelligence experience, sure, but we were just in Rome and there are a lot of things to do. Brotherhood is interesting, and it synergizes with Gather Support. The Consul should probably taken if we pick Loyalty. The Scipians is interesting, but I think we get more out of just talking to him. Still, if we want to go all in on figuring out Scipio, then it synergizes with The Consul and Loyalty. I don't think Sparring is worth it. Personal combat skill is nice but not worth it, Atellus is already in good shape, and is about to get a lot of experience from battle. I have a special place in my heart for Seafaring, but it's either going to be completely useless or absolutely amazing. If the best the Romans can put forward is 4, then not a lot of time is required before we're unbeatable on the sea. Not sure how often it would come up though. Para Bellum is a solid choice, in my opinion, we'd be studying older Greek tactics, but we might still get something out of it. Res Publica is even better than Para Bellum, I think, as knowing how to fight other legions is invaluable. The Cult is an interesting choice, and getting the officers to see things our way is important. Speaking of the officers, Fortune's Favor gets us in with important members of the legion, another solid choice. Study seems good, if a bit vague on what mechanical benefits we'd gain.
A tentative plan, but I'd love a way to justify taking Seafaring. I think there are a lot of good arguments for other personal actions, though. I kind of want to fit The Consul in, even if I don't think it's necessary. Swapping out Fortune's Favor for The Cult could work. The Cult feels more powerful if we choose Loyalty or Discord, though, and it seems a bit conspiratorial.
[] Preparing for Asia
-[] The Marians: You wish to know if Cinna or his allies are planning anything before they do it, and to receive updates on their moves and strategies, that you might better plan your own actions in accordance with what they might do. (-10 Talents)
-[] Theo: A young Greek with happy eyes, Theo was a slave, then a gladiator until he lost use of his right arm. Useless as a fighter or a worker, he was tossed aside to die, but instead came to your father's attention due to his particular skill with people. To put it simply, one cannot help but be charmed by him, from the shine of his teeth to the twinkle in his eye. Your father would send him to the markets to buy a cartful of grain, and the Greek would return grinning with ten for the same price. The servants skip to do his word, if only because disappointing him would be like pissing in the eye of the sun itself, and he is capable of winning a smile from even the most dour and grim-faced of men.
-[] Gather Support: Sertorius may be gone, but you are still here. You reassure the men's worries and fears, and promise that if nothing else, you yourself will lead them to glory and wealth in the hills of Asia.
-[] Res Publica: You study the formations of your own legions, the way Romans fight. After all, you may soon be doing war with Romans -- and what is more Roman than that?
-[] Fortune's Favor: After camp is made for the night, several of the officers, including Carcellus, Pompolussa, and Mercator, gather to gamble and game. They have extended you an invitation.
-[] Si Vis Pacem: You begin brushing up on your Greek, in ancticipation of subjugating Greek towns and villages in Asia.
Edit: And because I didn't really talk about where to put the bonus experience, my vote would go to Logistics and Engineering. They're both low cost for good benefits. Alternatively, we could save the experience for Seafaring, my true love.