I'm too lazy to write a guide, but here's some advice:
1. Don't colonize, build Greek Client Kingdoms or at least Client Kingdoms. They tend to provide better units - the Freed Slave Phalanx which you will get with Empire of Pontus is worse than the Macedonian Settler Phalangites. Also, the Pontic Lancers are not so great, you can get good cavalry from the galatians in Ancyra.
2. Get heavy infantry as soon as you can. Your Kardakes Hoplitai don't stand a chance against phalanxes. Try to get Ionian Hoplites or Macedonian Settler Phalangites.
3. Don't conquer Mazaca, it seems the Seleucids are obssesive about it and they will attack you even if you are allied just to get that city. Also, the Cappadocian Lancer, which were my main reason for hetting Mazaca, are in fact not so great (once again, the galatians are the best).
4. Don't focus on the Black Sea harbours, some of the inland provinces can give you better incomes with Regional Traders and mines.
5. Recruit mercenaries instead of regular units, when possibile - they're more expensive, but your manpower is very low in the beginning.

Here's a screenshot of my empire after almost 100 turns - I think I could have done better if I managed to keep at peace with the Seleucids and instead fight the Greek cities.
Click image for larger version. 

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