Good choice, AoM is a classic.
Was never exactly a pro at it but I played it a lot and can give some tips sorted roughly in order of importance:
- Its important to always have a lot of villagers, starting from fairly early on. It might seem like a drain on your resources but they make up their cost in food very quickly. I'd generally finish first age with around 10 and keep building more into the second age, ending up with at least 20 altogether.
- Get out of the first age as quickly as you can and try not to stay in the second too long, if you can advance ages about the same time as the other guy you should be good. You should start getting upgrades at the Armoury once you have a decent sized army sometime in the second age, around 12 guys or so. I generally upgrade hack armour first then weapons then pierce armour. At this stage you should also be thinking about creating another settlement and a bunch more villagers to go with it, around 5 or so.
- Food is generally the most important resource but gold also becomes very important the further you get into the match, especially for the Greeks. You'll always need wood but generally not as much as the other two. Try to always have a couple villagers at your temple generating favour, but it isn't hugely important unless you want to get a lot of myth units.
- All the Greek gods are pretty good. Poseidon is perhaps best when starting out since you get free militiamen whenever you lose a building and while his God power is pretty boring it greatly speeds up food gathering early game. Zeus gives some nice bonuses to infantry and a health upgrade to Heroes. Hades get you Shades and my favourite God specific fortress unit which is pretty much a siege archer. Choose whatever Gods work for you but try to avoid picking one that doesn't suit your playstyle just for a single unit or power, the upgrades that different Gods offer are also very important.
- When it comes to units you can always rely on your basic barracks infantry for most situations, though avoid Peltasts unless you keep coming across lots of archers. It's often good to have at least a third of your army made up of Hoplites and also a good number of Archers. I never worried about building cavalry too much as Greeks but if you do be sure to grab Dionysus as a minor God for some nice bonuses to them. Poseidon also gives Cavalry bonuses.
- Greek Heroes are fairly difficult to use as they are expensive and get taken down by packs of non-Heroes pretty easily. They are however excellent against myth units so have your Heroes avoid regular units while hunting down myth units whenever you can.
- Avoid maps with a lot of water when starting out. It's difficult to manage building and upgrading a decent fleet alongside your army and economy.
- Don't rely on walls and towers too much, soldiers are far cheaper, can usually be replaced easier and most importantly can move. If you do decide to make fortifications make sure you have the resources to do it and try not to let it distract you from building a proper army and gathering resources. Walls and towers can be good later game with a lot of upgrades but doing that takes a lot of resources you're probably better off spending on other things. That said Hades gives your buildings health and damage bonuses as well as Sentinels, so if you do want to go heavily defensive he's your best pick.
When it comes down to it, the best way to learn is to play. Get to know some different Gods, army makeups and whatnot and see what works for you.