The Second Fleet starts the game with relatively few resources, but it has excellent geographical access: it sits in a valley that extends through both the southern and northern hemispheres. It also has the most balanced portfolio of Utilities at the game start. It begins with a Farm and an Energy Mine, and it is close to the F-zone, where it can establish a supply of W. It therefore has a realistic chance of becoming economically independent.
The Second Fleet faction begins with the largest military force on the planet, but it is in danger of being overtaken by the UE faction, which can usually outspend it. SF should therefore try to use its initial military superiority to seize the means to grow its economic engine. It has a shielded E mine in its home base, and it can usually push north to seize the abandoned E mine at C6. If the Second Fleet does not establish itself in the north with some haste, it may find itself facing an expanding UE capable of matching SF militarily. If this happens, SF will need an alliance with AI, at least temporarily, to contain the hostile UE. Conversely, if it befriends UE, the two are likely to achieve rapid military dominance of the northern hemisphere, ready to push south to obtain water.
The most important early diplomatic goal for SF, then, is to avoid being the odd man out in the triangle of AI, UE and SF. The AI faction can build automated Units, and the UE faction can finance it, so an unwary SF may find itself facing a strong military pair to its north east. It should offer its military support to at least one of those factions and demonstrate, as soon as possible, that it is more useful as an ally than the competition.
Another early strategic decision for SF is what to do about its water supply. With the end game in mind, SF should consider whether it ultimately wants to ally with Cryos (providing the E and F in the final scoring while Cryos supplies the W), or push south to challenge the Cryos monopoly. If it does intend to push south, it will need cooperation from at least one of the other equatorial powers, FF or AI. It will also need to manipulate the balance of power in the hope of preventing any equatorial power from allying with Cryos. That may be difficult to do if SF has already displayed overt cooperation with UE.
Second Fleet holds one important Skill Card at the start of the game, Mech Master. This card provides a discount on Mechs. It is most valuable if used to build a large number Mechs, so it should be held until SF has a decent stockpile of Energy.