[X][PRIORITY] Seyek - identify and fortify blocking systems between Rethelia and the Bajoran/Cardassian border
[X][RISA] Assist in a refit program (+1S, P, D) (-15rp)
[X][AMARKIA] Focus on more next-gen frigates
[X][CORE] USS Lightning
The Vulcans have the lowest income of the original four, so an Ambassador is probably out of their current price range. They lack any Capitals, so an Excelsior-A is probably best they can currently handle.
The Andorians will have to spend a couple of years building up a resource stockpile for their Ambassador.
Tellarites have quite the resource stockpile, they can begin their Ambassador as soon as the plans are released to the members.
The Humans could begin their second Excelsior-A right now if they wanted, as they have not done so yet, maybe they are wanting to start their Ambassador first? Or maybe they have started it, as they only have one 3.1MT berth free, and I don't know what they are building in the other.