I have played this game 4 times over the past 2 days. (Yes, it is that good.) Here are my initial impressions of strategy. First of, everything in the game is useful and there are multiple paths to victory. I have used a different strategy every game so far and won 3 out of 4 (lost 4th on tie-breaker, grrr). However, I am certain I have not even begun to understand the true depth of strategy this game allows for. Anyays, here are my initial revelations.
Getting to the 3rd level of any area is key. It costs 3 spice & 3 boats which can be paid for from the initial boats, 1 colony & 1 plantation. This allows for 3 boats, which is enough to get another item to the 3rd level, refills 4 spice, double level 2, 8 money, always nice, draw 2 & keep 3 cards, very powerful. The only exception might be the colonists, here level 2 is needed, but level 3 saves you a person in founding a colony and thus makes it easier to found future ones.
It's all about the extra actions! In a 4 player game you are guaranteed 24 actions, assume 2 from winning the flag, 2 from getting everything to level 3, & 2 from winning auctions and you have 30 actions in the game. Now, if you can win the flag, get to level 4, or win extra action auctions you can get more actions. And every action is 3% more than you opponents will probably have. However, extra actions aren't the only way to game extra actions. If you need boats and are going to use and action to get them but instead win an auction for boats, then you just saved yourself and action and thus gained one. This is what the game is really about. Maximizing the few actions you are given and using the auctions to allow you to use your actions for other things.
Finally, getting the 10 points in areas is key. You will not win with everything at the 4 level, that's just 36 points (including colonies). And don't underestimate the auctions for victory points, the 1 colonies, the most money, or expedition cards. Those points are usually what makes the difference.
So far I have begun to see certain areas that work well together. Boats/spices is nice. Get ships, refill spice, upgrade, repeat. The same for founding colonies & ships. Found colonies, get ships, upgrade, repeat. Expedition cards are very powerful once you get to level 3. You can draw 2 every turn and usually those 2 cards will save you more than the 1 action it took to acquire them. The money column seems underused. If you introduce too much money into the game, it reduces the value of taking the money action. However, it you win your own auction or let other people win theirs, then it takes money out of the game and in a cash poor game, taking 8 money for an action instead of 4 can be huge. If you can win say the flag and a tile every turn you should win by a landslide.
Despite all the options you have for you actions, I think the auctions are probably the part of the game where you win or lose. However, I don't feel I have played enough to say what is a fair value for certain tiles yet. However, I can say that the take 1 thing every turn tiles, the vice-king, and the 2 action cards are huge. Don't let these go cheap.
Goa is well on it's way to becoming one of my favorite games and I am sure as I play more that i will discover more strategies that work even better. I hope this article helps and look forward to input from other players. Enjoy your playing!