One thing I haven't talked about is how you actually build stuff. There are 5 types of materials you need in your cities: wood, wine, marble, crystal glass, and sulphur. Wood is available for you to set people harvesting on all islands. Each island also has one of the other four materials. Obviously, you'll need to get the other 3 materials somehow. You can hope that someone on a nearby island has then available (which I've noticed is rare, at least on the islands I'm on), or you can use the premium trader. The premium trader allows you to trade materials other than wood 1 for 1 for each other. Wood can be traded at a 2 for 1. You will have to pay 3 ambrosia to the gods for this benefit though. Ambrosia is purchased with a plus account. In my experience, I never found people offering what I needed for trade, so I didn't see any way around paying for it. Honestly though, ambrosia is relatively cheap. You can get 100 ambrosia for $14.95 (that's the smallest amount). There are also bigger packages that are better deals. If you manage it well though, you'll be able to build on 4 different islands so that you'll have one of each resource without running out of ambrosia. Ambrosia can also be used to pay for premium advisors. They make it a lot easier to manage your resources. When you start to get a few towns, you'll probably want to pay for them sometimes too.
On the whole, I'm really enjoying Ikariam. Because it is all real time, I can set my towns going, go back to my real job, and check in on my towns every so often. I will warn you that starting out is somewhat slow. Since it is real time, you can't just hit space bar to skip years. You'll have to wait on your population to build up, but it really doesn't take too long. I recommend you go check Ikariam out. Given that it's free, what do you have to lose? It is a great way to keep occupied during breaks at work without getting so addicted that you lose days of your life!