Hey Nigel,
Maybe I can help some. Being somewhat new to ancient war gaming I had the same thought as you. A guide of any sort would have been welcome.
I would suggest you read through the rule book before you build up any minis. You just need to read the first twenty or so pages. It will give you some hints as to how you should build up your troops.
You get bonus to certain stats and checks depending on how many minis are in a unit. The minimum for the bonuses start at ten minis in a unit.
All minis in a unit must have the same armor and weapons. Not every single model needs to physically represent this however, the majority should.
With just those two things in mind there is enough to build eight Gauls with armor , sheilds and swords , along with a horn and standard bearer making ten in that unit. The rest can be built for a unit of Spears and no armor with a horn and standard bearer as well. I would make sure the shields are all attached to minis from the same unit. Can’t remember the exact count as I am away from home at the moment.
The legionaries can be built as eight with pilum for one unit and eight with swords for the second. It’s odd you didn’t get enough swords and pilum. I have eight of each.
Lastly the reason for the horn and standard are that they too Grant you bonuses if they are in a unit. The horn grants the unit a third action per turn and the standard bearer grants a re roll on bravery tests if I remember correctly.
At any rate, I hope this helps a little and if you have more questions please feel free to ask.
