Playing as a non-Roman faction with this mod is far different than playing as one with just vanilla Rome 2. There are a few points you need to consider:

Choose wisely!
- With this mod, certain factions become considerably more difficult than what they were in vanilla. The Arverni, for example, are Rome's historical nemesis and thus, there is little you can do to try to cement an alliance with the Roman factions. You can either carve out a small empire quickly and hope the other Roman factions will be too busy to assist the Julii or you could pack up and move elsewhere!

There is little you can do to halt the expansion of Rome.
- All of the Roman factions will assist their Roman allies with each other's wars. Your best bet is to either ally with Rome or form alliances with other factions to bring down Rome together.

Ambush!
- If the battle of the Tuetoberg Forest has taught us anything, it's that the Romans are no good in an ambush. If war is inevitable, try setting up ambushes. You can crush entire legions with a good ambush while taking minimal losses. This will help in making the Romans weaker and susceptible to invasion.

The enemy of your enemy is your friend!
- Try supporting Rome's major enemies the best you can. Even if you aren't at war with the Romans yourself, sending a substantial monetary gift will aid them in holding the Romans back, even if it's just for a few more turns while you prepare yourself.

Cavalry!
- Rome is weak in the cavalry department. By showing up to battle with superior horse mounted troops, you can easily take control of the battlefield, eliminating Rome's missile troops and executing some damaging flanking manuevers.

If you have any other tips, let me know in the comments! Good luck!