A Quick Summary Of All The Factions

Roman bonuses

(+) +1 food in all provinces
(+) +1 experience rank to all infantry recruits
(+) starts with mount Vesuvius +3% morale for all armies and fleets, +2% wealth from agricultural
and livestock buildings
(+) Starts with "noteworty" imperium
4 starting regions
(-) Republic

Internal factions:

House of Cornelia
(+) 3% increase to tax rate
(+) a diplomatic bonus with all Hellenic factions (+20)
(-) reduced population happiness for latin culture (-4)

House of Julia
(+) +4 cultural conversion rate to Latin culture
(+) 10% increase to unit morale when fighting barbarians
(-) 25% increase to unhappiness caused by foreign cultures

House of Junia
(+) +4 to public order from presence of Latin culture
(+) 10% icrease to wealth from agriculture buildings
(-) -25 to diplomatic relations with all factions

Carthage

Faction bonuses
(+) 40% reduction to mercenary upkeep costs
(+) 10% increase to wealth from commerce buildings
(+) Starts with "noteworty" imperium
starts with 4 regions that are all separated by sea
Phoenecian culture but hellenic buildings etc.
apparently does not trigger Hellenic specific effects
(-) Republic

Internal factions
The Hannoid dynasty
(+) 10% increased movement range for armies and fleets
(+) 5 increase to biplomatic relations
(-) 10% increase to mercenary upkeep costs

The Mangonid dynasty
(+) 20% reduction to resistance from foreign occupation
(+) 5% reduction to unit (other than mercenary) upkeep cost
(-) 6% reduction to tax rate

The Barcid dynasty
(+) +4 population happiness for the presence of Phoenician culture
(+) 5% increase to wealth from agricultural buildings
(-) 30 reduction to diplomatic relation with other factions

The Greek states
Group bonuses
(+) +2 to cultural conversion
(+) 10% increase to melee defence when on own or allied territory

Sparta
(+) +1 experience for infantry recruits
(+) 25% reduction to discontent caused by slaves
(+) Starts with the Statue of Zeus at Olympia which grants 3% increase to wealth gained from culture buildings and +6 to public order from the bread and games edict
Starts with a single region
(-) 10% reduction to the wealth from industrial and commerce building chains

Epirus
(+) +4 happines from the presence of hellenic culture
(+) 10% increase to the wealth of minor settlements
(+) Starts with mount Olympus which gives a 20% reduction to happines penalties due to different cultures, and a 5% increase to wealth generated by cultural buildings during the bread and games edict
Starts with 2 regions
(-) 20 reduction to diplomatic relations with hellenic factions

Athens
(+) 10% increase to the research rate of technologies
(+) +1 to naval unit experience
Starts with a single region
(-) 10% increase to non mercenary unit recruitment cost

The Successor Kingdoms
Group bonuses
(+) 10% increase in troop morale when fighting hellenic factions
(+) 20% reduction to resistance to foreign occupation

Macedon
(+) 10% increase to troop morale when fighting barbarians
(+) 10% increase to wealth from industrial buildings
(+) Starts with The sanctuary of the Great Gods (+2 growth factionwide and spreads culture more rapidly factionwide (+3)
Starts with 2 regions
(-) 20 reduction to diplomatic relations with hellenic factions

Egypt
(+) +1 experience to naval recruits
(+) 10% increase to research rate
(+) Starts with The Necropolis of Giza 3% reduction to construction costs factionwide and +2% wealth from culture buildings
(+) Starts with The Pharos of Alexandria 20 increase to line of sight for all fleets and 5% increase to wealth from maritime commerce buildings
(+) Starts with 6 regions making up the entire province of Aegyptus and half of Nabatea
(+) Starts with "noteworty" imperium
(-) 25% increase to unhappiness due to presence of foreign cultures

Eastern empires
Group bonuses
(+) +1 experience for archer recruits
(+) 10% increase to the wealth brought by commerce chain buildings

The Selucids
(+) 10% increas to wealth from agricultural buildings
(+) 25% reduction to public order penalties due to foreign culture
hellenic culture
Starts with 6 regions making up the entire province of Syria and 2 other regions
(-) 40 point reduction to diplomatic relations with eastern factions

Eastern empires
Group bonuses
(+) +1 experience for archer recruits
(+) 10% increase to the wealth brought by commerce chain buildings

Parthia
(+) +1 experience to cavarly recruits
(+) 25% reduction to happiness penalties due to the presence of foreign cultures
Starts with a single region
(-) 25% increase to the unhappiness caused by slavery

Pontus
(+) 10% increase to troop morale when fighting barbarians
(+) 25 increase to diplomatic relations with hellenic factions
Hellenic culture
Starts with 2 regions
(-) 35 decrase to diplomatic relations with eastern factions

(look for Parthia in the Hellenic cultures (they have the Hellenic building roster))

Britannic Tribes
Group bonuses
(+) 10% increase to melee defence when fighting on own or allied territory
(+) +1 happiness across all provinces for every war with a neighbouring faction

The Iceni
(+) 10% increase to the charge bonuses of all units when attacking
(+) 10 increase to diplomatic relations with non barbarian factions
Starts with a single region
Extra region wealth:
Camulodunon +700
Celtic culture
(-) 50% less captives after battle
((-) starts with 2 mercenary spear bands, might not want to keep them around for too long)

Gallic tribes
Group bonuses
(+) +1 happiness across all provinces for every war with a neighbouring faction
(+) +1 experience for cavarly units

The Averni
(+) 20 increase to the diplomatic relations with other barbarian factions
(+) 10% increase to wealth from industrial buildings
Starts with a single region
Celtic culture
(-) 4 reduction to public order for the presence of celtic culture

Germanic tribes
Group bonuses
(+) +1 happiness across all provinces for every war with a neighbouring faction
(+) 20% increase to the income gained from raiding and sacking

The Suebi
(+) 3% increase to the tax rate
(+) 10% increase to troop morale when fighting barbarian factions
Starts with a single region
Germanic culture
(-) 25% increase to the public order penaly of foreign cultures

Nomadic Tribes
Group bonuses
(+) 10% increase to loot gained by raiding and sacking
(+) +2 recruitment capacity in the home province

The Roxolani
(+) 5% increase to wealth from commerce buildings
(+) 10% increase to melee attack when fighting in foreign territory
Starts with a single region
Nomadic culture
(-) 25 point diplomacy penalty with other nomadic factions

Royal Scythia
(+) 10% increase to wealth from industrial buildings
(+) +1 experience for archer recruits
Starts with a single region
Nomadic culture
(-) 25 point diplomacy penalty with hellenic factions

The Massagetae
(+) 20% increase to wealth from lifestock buildings
(+) 10% increase to unit defense when fighting on friendly territory
Starts with a single region
Nomadic culture
(-) 25 point diplomacy penalty with eastern factions