I won't say how many units and such that I used because it depends on your playstyle, fx I usually use small amounts of expensive units rather than have a ♥♥♥♥ ton mediocre units. I play defensively with pikemen and hoplites in low odds fights and use cavalry to take out ranged units if that helps.
Also try to make allies of all your neighbors so you don't have to worry about war on multiple fronts and split your armies up.
Here's a list of the factions that I had treaties with or went to war with.
Basically you just have to make friends with all the green smileys.
Also I was done around turn 13.

Research:
I'm just gonna list the research in the order that I did it, and it's only in the military section so you don't have to look around that much.

Logistics
Tactical Drills
Organised Supply
Military Settlement
Hellenisation

Immediately as I started I moved my fleet and my army located in Pulpudeva towards the town of Antheia in normal stance. After I moved them they were still in my borders so I increased the size of my army and fleet by a good margin, probably doubled them. Next turn I attacked the town and although the odds were against us I still won, I didn't lose any units but I did lose a lot of men.
Remember to treaty with your neighbors as well because it's very important, if you can try to make friends with the Odrysian Kingdom it'll probably make it easier but if not it'll be fine.

Next turn I moved my army towards Pulpudeva but kept my fleet in Antheia to help with public order.
The turn after that the Odrysians declared war on me and attacked Antheia, but they were dumb enough to attack it from the port without a fleet, so even though the garrison and my fleet was completely destroyed I still won because they only had transport ships and not battle ships.
Meanwhile I was moving my army down on Odessos about to take it, but the next turn they sued for peace and I moved my army back to Pulpudeva. Triballi had also declared war on them and they had a full stack moving down on them so I figured I'd let them destroy them and save some time.

Next turn there was a rebellion in Thracia, but the Odrysians were so kind as to attack them and my garrison helped to defeat them, and thus the rebels had been destroyed, in the same turn they had appeared no less.

Around this time Sparta had asked me to go to war with Epirus and I accepted. I moved my army from Pulpudeva down to Pella to give all it's best units to my main army and then moved it back to Pulpudeva. Next turn Triballi destroyed the Odrysians and I started expanding my army in Pella.
One important note: You should probably upgrade your barracks if you haven't already.
When I had a good amount of units I moved over to Apollonia in normal stance, Epirus only had a small fleet there and both their armies in Larissa.

Next turn I took Apollonia with relative ease, and Epirus besieged Pella. But instead of hurrying to the city's aid I moved my army south towards Larissa. I figured they wouldn't take my city because it had a very strong garrison and could probably fend off the attackers without reinforcements.
The next turn I took the town of Larissa and subjugated Epirus which obviously made them stop their siege.

Now the fun part, subjugating the Spartans.
I moved my second army in march stance down towards my main army. I replenished the units of my main force for 1 turn and moved down to Athenai, right on the edge of the border to Sparta and declared war on them. As expected they attacked me with all of their strength, they had about 1000 more men. But with a good defense, a strong line of pikemen and some harassing cavalry I beat them with acceptable losses.

Next turn I moved my second army right next to my main army and waited 1 turn to replenish my troops, but you won't be able to do it for longer or else Epirus will attack Sparta.
When my men were ready I attacked Sparta's capital... Sparta.
T'was a tough fight but we came out on top (gachiGASM) and took the city, and then subjugated them, and in doing so got the achievement 'A League of Their Own'.
Though you do have to hit End Turn before it gives it to you.
In the end your map should look something like this :)