Some tips i have learned for non-team games on this map are:
example - colors: red owns south america (sa), green owns north america (na), and blue owns africa, yellow owns oceania, pink owns europe (eu)
1) (red, green, blue, and 1 other necessary) Once u control ur country, a good strategy is to kill red's armies in asia, because now they will have a very dificult time getting cards, and for pink or yellow, you have also forced red to place his armies in sa, both eliminating a posible threat, and weakening blue and green (who are forced to protect themselves from additional red troups in sa).
2) (red, green, blue necessary) If you are red, make sure to have at least some armies in asia for the reasons in #1, unless you can easily attack green or blue.
3) (red, green, and 1 other necessary) It is often very easy in the early game for red to take Mexico, thus preventing green from taking Na, and can generally hold it until much later in the game.
4) (green, and 2 others necesary) if you are green and if there is no red, or he is very weak, NA + SA is a formidable combo, +7 troop bonus, and still 3 entry points (2.33 troops per entry point)
5) (long games) On south america, it can be effective to defend ur border if you place a few troops on Sao-Paolo, and Bagota (10-15ish), and stack a lot on Lima, because people will be hesitant to unleash the massed army gathered on Lima, this can also be effective in europe, with small numbers on Moscow, Itsanbul and Madrid, while stacking on Berlin, and Reykjavik. One problem with this strategy for europe is that people on Oceania, or SA can attack you while u have a limited ability for counter attacks.