Good luck getting your friends into the game!
However-
Grass4hopper wrote: (All three companies will be clone to start with.)
I recommend against this, the game is designed for the forces to be unbalanced, both set up (deployment), PPA, and initiative (determined by score) reflect this. The Primary Defender is supposed to be "underpowered" and thus gets a point bonus and more control of set up. While the Attackers are more powerful, and as a result pay a penalty in PPA and have less control over deployment.
Depending on your groups experience with wargaming, you might want to try Lumpley's
Demo Rules for a first game. If I were going to make 3 forces designed to be used more than once to play each other, I would probably have them something like this:
Defender- 4 Frames, all have full systems (16) PPA=7. Starting score with 2 stations is 42
x1 Soldier
x2 Delegator
x1 Charger:

,

,

,
Secondary Attacker- 5 Frames, 2 have full systems, 3 have 3 systems (17) PPA=5. Starting score with 2 stations is 35
x2 Soldier
x2 Mini-Soldier:

,

,

, (free)
x1 Armored Spotter
Primary Attacker- 5 Frames, all have full systems (20) PPA=3. Starting score with 2 stations is 21
x2 Soldier
x2 Brawler
x1 Commander: Split

/

,

,

,
As you can see, the Defender starts with twice the starting score of the Primary Attacker, suddenly being a frame down doesn't look so bad! Also the Secondary Attacker has a distinct points advantage over the Primary Attacker, showing the advantages of "underbidding". Yes, the Defender has everyone gunning for them- they must be cunning and get the others to fight each other. And yes the Attacker has a steep uphill climb- they must be aggressive! After the first game, have eveyone play a different force so they can see how the different deployments work. If the Secondary Attacker is winning too much, you could knock them down to 5 Frames, 1 fully loaded, 4 with 3 systems.
Both VictorFaria and Blorf are right on about loadouts. I recommend giving Blorf's Commander's Handbook a look.
Some thoughts on loadouts-
The Soldier:

,

,

,

, is very versatile and more powerfull than it appears, being able to use 3d6 for whatever action you deem most important that turn (useing white dice).
The Delegator:

,

,

,

, affects the flow of the battle by forcing enemy frames to activate, and laying big, juicy spots to encourage damage where you want it.
The Brawler:

,

,

,

, (free)

, is in my opinion one of the best loadouts of the game. The

terrifies opponents, the double blue protects the frame and it's close support, while it gets to use the free

effectively giving it 5 systems!
The Armored Spotter:

,

,

,

, is unnasuming and often ignored, but the double yellow effect can't be! High spots are what ultimately cause the most damage through the game. Meanwhile it has the

to discourage attacks and gets to use the free

, making it as well equipped as many 4 system frames.
So obviously these are just my opinions and suggestions, feel free to ignore/change any and all of em.
Hope this helps!