Thanks for the response. It's kind of weird that the units are listed as unique. Most of them are generic type creatures for the most part. House ruling it would be fine I guess. Well now I have a reason to get the exclusive Walmart version of the base game if I want to lol. I mean right now we only use Kiora in one on one battles for the time being and just use the single colored walkers for anything more. Obviously black has to pick one of the other to play.
Another thing I was thinking about doing for now is just treating Kiora as another blue OR green walker. So technically green/blue/black all have two options this way Kiora only ties up one color and not two. I'll only do that until I can afford more sets if I follow through with that.
On the Unique Front; Rumor has it that the Innistrad Expansion coming this fall with include common squads for each color.
On the Kiora front... Yup, 2nd base set is your best bet. Keep your smartphone handy when you go to check out. The online price is usually a few bucks cheaper (24 right now, it's been as low as 18)
The other thing I'd highly suggest is biting the bullet and snagging some Heroscape terrain. You're looking at ~$40-50 for a 'RoTV' worth of terrain. Which is Rise of the Valkyrie, the 1st HS core set. It really brings the game to life aesthetically and strategically.