Have a read of this
viewtopic.php?f=341&t=78101 on escalating games.
What you are generally trying to do in escalating is not occupy continental bonuses, but to be in a position so that you can, at the right time, eliminate a weaker player and steal their cards; if you do so, and your card total during your turn is 5 or more, you can cash in again (and the cash-in value will go up accordingly).
The best players look to sweep the board by positioning themselves so that when cash-ins are at a level that allows them cash to eliminate a weak player, they get enough cards to eliminate the next player (and take their cards) and so on until they have swept the whole board.
It would also be legitimate to eliminate a player even if it won't let you sweep so as to prevent one of your rivals who could from getting their cards.
I have gone off on a bit of a tangent (read the link above which explains what you are trying to do in escalating very well) from your game.
In a 5 man manual deployment game like yours however I would take Oz and I would be using the bonus in the first instance to keep Red from taking Europe. You will also need to watch for green in NA. By the time he conquers that though, presuming Blue fights from SA, the cash in values will probably be getting high enough to influence/decide the game.
More importantly enjoy the game and the site.
ps can I ask how you found that game in the first place ?