1. Ignore who you are at war with. They probably won't come at you right away.
2. Don't target the two small states up in the mountains. It takes forever to get there, that will cost endless resources supplying the armies, and they give you very little.
3. Think historical. The Romans expanded on the western plains for a reason:
...Latins provide wood...focus them on that and growing the city larger
...Hernici provide iron...same
...don't grow more farms at Roma...you need the space for troop improvement/types...Roma recruits your armies...so build here to improve your troops and get the population up (leave people NOT working so they...uh...well...spend their idle time effectively!
)4. So...target Caere (closest,easiest target) and Falerii...main product...food
5. Once you have these two (and you first need to build some troops...don't be in a rush) then expand north or south but not west...south is probably easier, but be warned, the states will have large armies!
6. You can eventually move east, but it becomes more dangerous (harder for you to transfer troops about).
7. Don't be in a rush.
8. Build only in winter (unless resources are piling up). At the beginning of every spring, check each city and set workers/population as needed. Keep armies in cities until the time you are set to invade.
Move on to Summer 367BC and see who is at war with you. This time around it's the Caeretans, Aequians, and Volscians. Definite squeeze! We will just sit tight and build up resources. Check each city and make sure production is worked to the max! By winter, nothing much has happened. We build a FORT at Roma, and we increase the size of production at the other two cities to large versions. You could pass on the FORT and just increase FOOD production at Roma. If you are feeling nervous about your neighbours, you could shift some troops from Roma.
Winter 366BC: Large Farm at Roma, Outcrop Mine at Hernici + 2 Auxiliaries. My lack of FOOD production is showing! Perhaps that should have been first at Roma.
We have also moved some troops from Roma to Latins in case our deluded southern neighbours get early ideas.Winter 365BC: Farm at Roma, Lumber Mill at Latins. Hopefully next winter sees building of new legion at Roma and preparations for war.
Winter 364BC: 2 Legions recruited at Roma. The forces at Latins had moved back to Roma. We will send excess troops back to keep the southern enemies cautious.
By Summer 363BC we are moving on Caere. Are we too early? Should we have waited at Roma and upgraded before invading? We shall see! (I saved!!)
On the battlefield, we keep our best troops on the left, aiming for the open ground. Our centre/right is given orders to hold and then advance, hopefully with the left flank coming down to help. Unfortunately, they do just that!
And the actual. Lesson learned even though we win: Build up those troops and bring more than 1 Auxiliary along!
We will spend the next few years upgrading troops and cities in preparation to invade our second initial target. We've captured Caere in Winter 363BC just in time for builds! 
Winter 355BC:
Phase One of the unification is complete: Caere and Falerii have been taken. The army that captured Falerii will remain there as protection against invasions from the north or east. We will spend the next few years ramping up production and building a second army to head south. Production is already coming along nicely (see last screen shot below).
We assume there are not too many of the enemy this time.
Left flank surges forward and overwhelms.
Remainder of enemy encircled and routed.
And production at this point:
