I don't know how much you have available to you, but I can recommend the Day One adventures to you.
It is a set of unconnected adventures....all set on Day One of the invasion, and each one shows off a different invading cosm. The way they are laid out is actually sort of like a videogame tutoral, where they introduce concepts over the course of the adventures.
This serves three good purposes...
1. The players get to learn the very basics of Torg in Adventure 1, as well as learn about the Living Land.
2. The players add in spellcasting and magic items in Adventuer 2, as well as learn about Aysle.
3. As a GM, you can get some practice on picking up the "feel" of each cosm and learn how each of those areas lend themselves to different styles of gamemastering.
Each adventure has prewritten characters that support the stepped learning. The characters are interesting and the plots of the adventures are mostly straightforward, but allow the players to explore the different environments. There are a lot of "Oh cool, check this thing out" parts of the adventures (like a certain magical ring from a famous fantasy movie being in a movie prop exhibition of a museum...which then transforms to Aysle with expected results).
The Day One adventure book will really help the players decide if the game is for them, and which parts of the game they like the best. Then you can focus on those things for your campaign.
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It occurs to me that its never really said outright, but one of the tricks of running Torg well is to remember the genre of fiction the different cosms represent and ensuring that you GM through that filter. In the Nile Empire you should run your games like an Indiana Jones movie. Car chases, lots of easily dispatched bad guys, hidden temples...etc. In Pan Pacifica you have the obvious ninjas and robots and mechs...but you also have the "trust no one" triple-double-agent corporate backstab elements as well.
I ran an entire adventure in that cosm that was simply the fallout of one of the PCs being hired to snipe a corporate turncoat from a hotel. After being tricked, spied on, and used by no less than 5 different groups before their mission ultimately failed they left the area and vowed that it was "the worst place on the planet" because they literally couldn't trust anyone. Players have a general blind-trust of the mission giver NPC or might suspect them of being an evil mastermind...but they NEVER expect the mission giver NPC is just hiring them for someone else on behalf of a third party who is at crossed swords with another corporation who is trying to turn the PCs back on their mission while a third unrelated group is manipulating them against the original two.....on and on. THAT can be the feel of a Pan Pacifica adventure, totally at odds with tomb raiding and running from giant rock ball deathtraps.