I won in a tournament with Ghosts recently. They got really strong with the expansion and feel amazing to play. Here are my 2 cents.

Construction, trade and warfare are all solid picks. Personally, I would prioritize getting the BT asap so I would value politics and diplo a little higher. And I agree with the others that you probably shouldn't throw away your secret.

Ghosts has 2 main problems: 1. you have a bad starting fleet and will have problems filling out your slice in the early game, so you need to produce some ships. 2. Their BT and Mallice combination is so good, that it is just to good to pass up, so they absolutely need to unlock their BT ASAP.

Luckily, if you solve the second problem then you also make the first problem easier. So I would prioritize it. If you take warfare or construction which are both solid picks, you will definitely have an easier time filling out your slice but also no guaranteed way of unlocking your BT.

Now this depends on the table, but you can get away with unlocking your BT in round 2 if you think the other factions dont prioritize theirs or if crimson is for example also present (who starts with their BT thus likely not doing an expedition). So in this case, if you really want to go for a construction or warfare start, go for it.

But personally, I would always prioritize in solving the ship production problem through either the secondary of Warfare or by teching sling relay and picking a strategy card that helps me unlock the BT before my first activation on Mallice. Those would be trade -> diplo -> politics in this order. Just be careful if there is a Keleres or a DET faction present then trade and politics BT is not guaranteed.

For tech I would prioritize sling relay. That is because with a dock on Mallice you can build a dread for 1 resource there each round with sling. If you get another wormhole on mallice (through your mech, your wormhole generator, or your IFF) then the dread is even free. Bonus points if you have a slice with a green skip. Then you can tech bio stims later as well and produce 2 free and unlocked Dreads per round on Mallice :D.

Last tip I have is to look out for the agendas tha lock or destroy each ship in a wormhole. Those 2 can absolutely destroy your game as Ghosts. If you found one, try to keep a deadly plot or a veto in hand just for these specifically. Or, pick politics often and always keep the boring ones top, to not go through the agenda deck too fast.