General path

The farming path
buy the 3 cheapest gens and do mission, upgrade the senate and wait till you can pay top tier gens

the allround path
buy pacorus I, then cleo and lv your commander in inf don't give him inf skills because we're going to switch him to archery 5000 looks like much but's only two times auto-massylii. Then you buy vercingetorix after him buy arminius then mithridates VI. Now you have 2 inf, Cav and two archery. Then we buy scipio, Pompey and then Octavian. And in the end you buy Huo, Antony and agrippa.

now you have:

inf 
-vercingetorix
-Pompey
-agrippa
-commander

cav 
-arminius
-scipio
-huo
-antony
-pacorus I

archery
-Cleopatra 
-mithridates VI
-Octavian

we change our commander to archery/navy with archery skills
and sell pacorus for Who you think is the best forth inf gen.

set 4-4-4-2

the Cav way

first buy pacorus I then Commius now you have two decent Cav gens, as First top tier you shouldn't buy arminius the best Cav Why because more then two Cav units in campaigns I rare that's Why you buy mithridates VI First, then arminius and then vercingetorix. Now you can buy Scipio, Octavian and pompey. Now buy Huo then who you think is the third best inf, i took agrippa in allround because he's a good navy hybrid but this is the Cav way we don't need navy. Then sell pacorus and buy Antony and tiberius. I would upgrade my commander in archery but you can also do it in Cav,

now you have 

cav 
-arminius
-scipio
-huo
-antony
-tiberius
-Commius 

inf 
-vercingetorix
-pompey
-Who you think is the third inf

archery
-mithridates VI 
-Octavian 
-commander

3-3-6-0

the archery way
first buy cleo try to get mithridates VI then it could be a pain but if you just do easy conquests it should be possible now buy arminius and vercingetorix. Then Octavian, scipio and pompey. Then Huo or Antony Who you like better and Who you think is the third best inf gen. Then get Surena and li. Upgrade your commander in archery/navy.

now you have:

cav:
-arminius
-scipio
-Huo/Antony

archery:
-mithridates VI
-octavian
-li
-surena
-commander
-cleo

inf:
-vercingetorix
-pompey
-Who you think is the third best inf

3-6-3-1

the inf way
first get trebonius then bato. Then get vercingetorix, Why? Because you do get enough inf units. Then arminius and mithridates VI. then pompey, scipio and Octavian. Then get labienus and Huo or Antony Who you think is better. Then sell trebonius and buy labienus, crassus and Burebista. Upgrade your commander in archery/navy.

now you have:

Archery:
-mithridates VI
-Octavian 
-commander

cav:
-arminius
-scipio
-Huo/antony

inf:
-vercingetorix
-pompey
-labienus
-crassus
-Burebista 
-bato

6-3-3-0

Explanation:

why do I keep my First gens So long?
because it's useful to have more gens for missions

why do I in all the paths upgrade my commander in archery?
because I think that archery has the worst third gen: Surena/li
while inf got many options and Cav has Huo and Antony.