The theory is pretty simple: gift early, expand concisely, bugger the Island of the Giant's AI and screw up the East City AI by first turn hopping around toward the commander. Commander hunting, as usual. Dance into the west part of the city while clearing out Island of Giant's holdouts in the west.
Keep in mind, the gold star it comes to hunting then north west city AI's leader and killing him n time frame. Sometimes he hides in the top corner, sometimes in the tower, and sometimes he just runs central. Keep a plan for each of them. You'll win 90% of the time, but gold starring can be a little tough if the commanders get a bunch of obnoxious first jumps/your AI buddy is picking his nose.
Turn one: 3 to eastern spawn, take Farm. 2 to western spawn. Send leader alone to Little Ivywood, leave the two still.
Turn two: 4 to eastern, take Garden and Summerford. 1 to western (stack on the two from before) take Dustmead with leader, Far Water with troops.
Turn three: Gift Summerford (can gift now or delay one turn, but I prefer gifting now). 6 east (Stables), take Corness and Lorburn. Pull your troops from Garden upward. 4 west, take Hushwald and Dewhurst. Send leader alone to Trapper's Trail.
Turn four: 5 east, take Blue Bayou bonus and Shadowbeach. Move the 2 in Farm to Stables. 5 west, take Silent Army bonus and Northern Wasteland bonus.
Turn five: First contact! 15 east, to Shadowbeach. Last move, take Santa Maria. Position troops to have 3 in Ironbeach and Corness each. 2 west, take Aylesbury and Ormskirck. Move leader to Rochdale. (This is preference. Could send 14 east and the extra to Sparklower to hit Matlock for equal power).
Whatever happens in the Santa Maria defines the rest of the strategy, but, as usual, it's about commander killing and positioning. If you can take Santa Maria, split forces between Island of the Giant AI and eastern city AI. If he bounces you, take it next turn, but your gold star is probably gone. First-turn-hop around and bonus break while you home in on the commander, attacking with ~11 in the eastern city, everything else toward battling Island of Giant/expanding (eastern city is usually in Temple Hill or running toward Quarly, depending on how your buddy is doing, Giant Island commander is usually on the western side. Pursue him hard.)
When you find them, hit for commanders assuming that they'll reinforce by 5.
Positioning is the important part against the north western city AI if you want the star. You want to slip a troop in through the breach and through the ship and pincer in, shattering bonuses as you home in. Even if he has a stack that can beat you, you can often delay to the end of the turn and slip in right after him. Pick up Northern Forces when it's available, but if your commander hunting goes well, you dont really need it. You have about a two turn margin of error for the star. You need to be pushing a fastest route toward the corner/tower part of Northwest City as much as you can. Very easy to win one turn too slow.