OK, I've watched your replay now, and this is my personal take on things. Keep in mind that I've only been playing about two and a half weeks. While I feel I've learnt a lot about the game in that time (and especially about playing on Emerald, since I'm still only a trial player), and I've had victories against some fairly strong players, Artanis is obviously a much more experienced player; anywhere that his/her advice contradicts mine, s/he's almost certainly the one that's right.
I felt your initial deployment was too ambitious. Deploying against the High in the northwest corner was good, but deploying against the High in the northeast as well was a bit reckless - if your opponent had played more aggressively (and you should be expecting this since you were F.N.U.), you would have come under a lot of pressure. You were also very lucky that the northernmost of the two central Low economy countries was a Neutral and not an Enemy Secret Ally.
The main thing I'd change would be to deploy your central northern Low Ally against that adjacent, north-central Low instead of the northeastern High - simply deploying to cover the border against that high.
I do think you chose the right two SAs to deploy at the start, though. The other main alternative I see would be to have deployed your High against the Low in the southwest, planning to push east through the southern areas of the map with the help of your south western Low SA, along with your northwestern Low, either against the High, or the north-central Low. I favour the High, it's riskier, but worth it, and the chances of a Red disclosure of the northernmost of the two central Lows (which actually turned out to be Neutral in your game anyway) on the first turn is small, since it was not well placed to safely invade anything given the likely locations of the Enemy Secret Allies.
Fortunately, your opponent's deployment was worse. S/he wasted $4 on superfluous Smallfoots in the Low, and deployed badly in the High as well, wasting money on another unnecessary Smallfoot, and failing to deploy a transport with the troops there.
A deployment of tanks with a transport in the Low, and two Pteroplanes (since s/he seems to be fond of them), with another transport and two tanks in the High could have taken the capital of your Low SA, parked two planes in it (safely, so long as a tank and not the transport held the capital), and delivered five tanks there as well. I can't see how you'd have been able to hold onto it under those circumstances, especially since s/he had another adjacent SA.
I'm not really sure if planes would be a good idea or not for that deployment, but since the High is "red-locked", they seem like they should be a pretty decent choice, at least. It could be used as a plane factory for both fronts.
Since you had deployed for it, and your opponent had deployed unambitiously, you were right to press ahead and invade both the Highs you had deployed against.
However, you should not have disclosed your Low SA that was invaded on the first turn. The location of your High was obvious already by then, and you should have disclosed that first, only disclosing your Low SA when you could be sure of holding it. With better play, even despite the initial deployment, I feel your opponent would have taken your SA, and with the resulting indemnity won the game, pushing on into your High and striking up through the center at your exposed southern flank in the north.
Your opponent played much too slowly/passively throughout the game, and basically handed it to you on a platter. The guerilla deployments in both invaded neutral Highs could have been better (in fact, I think s/he should have been able to hold the northeastern High a lot longer, and maybe even indefinitely.
You made much better use of transports, which was vital since almost all your forces were slow moving. You may have had slightly too many of them, but I'm not really experienced enough to say.
Your opponent failed to do anything very useful with his/her central Low Ally. S/he needed to either deploy heavily against your Low Ally in order to win it quickly, or deploy against the Neutral Low to the north and attack your southern flank (which I think would have been best). You may well have been able to hold on that front, but it should have prevented you winning in the northeast, at the very least. Instead, a lot of troops just sat there idle while no progress was made.
You did a good job holding onto your Low SA in the Southwest. In the northeast High, I think the instant you gained control of it you should have moved your troops back west and then pushed south into the Neutral Low on your southern flank to open up another front in the south and take control of the battle there. It's difficult for you to make progress south on the eastern side due to the narrow pass, and the northeastern High is more than capable of holding that pass on nothing but its basic income.
That's about all the advice I have. Congratulations on your victory, and thanks for posting an interesting replay. We can always use more replays on the forums, and I hope you'll post some more of yours in the Replays section in the future.
Incidentally, my name in the game is the same as on the forum here, so if you want a reasonably challenging game (Emerald only, since I'm trial for now), feel free to challenge me.
(I'd also appreciate comments from Artanis or others as to where I've gone wrong in my commentary on this game.)