I don't know the battlegroup rules, so can only infer from other's comments that you are looking for fire-team basing for your figures.
I use US 1 cent coins for my basing. I find them to be cheap (I get as many as 100 for just $1 USD!), and always available. That last part, availability, is one of the key advantages, as there are few things I find as frustrating as running out of bases on the last one or two stands I'm trying to complete, and having to wait for the purchase of more of my whatever-they-are bases to be available to finish the unit. With pennies, I can just go lift up a cushion on the couch and always find a few more.
I also occasionally use Euro 1 cent coins for some of my smaller bases, particularly for command stands. Being smaller, they are useful for 2-man units, but alas, they are not nearly so readily available to me, and having 2 figures on a stand is enough visual distinction that I don't really need a smaller stand.
In the rules I use (Mein Panzer v2), the infantry is squad-based. Most stands represent 8-12 men, regardless of how many you put on the base. Some stands represent half squad-sized "teams" of 3-6 men.
For my forces I use a standard presentation of 4 figures representing a standard rifle squad. I usually put 2 rifle figures and an LMG team on the stand. Some WW2 armies (Italians, Soviets) did not have LMGs in every rifle squad, so in some cases I just put 4 rifle figures on a stand.
I put 3 figures on a penny to represent a full squad-sized unit (ie: 8-12 men) that is not a rifle squad. Such a unit might be a larger HQ, or combat engineers, or a heavy weapons crew, or any group of specialist troops.
I put 2 figures on a penny to represent a half-sized unit. These might be LMG teams, or command stands, or commo teams, or FO teams … whatever would be less than a full squad in size. Here the figures themselves are more important to determining what the half-sized ("team") stand represents.
Some examples:
Here is an infantry squad from my WW2 Romanian force. Here you can see the squad includes riflemen and an LMG team.
Here you see a platoon of my WW2 Romanian infantry. There are 4 rifles quads (Romanians had larger platoons than many western armies), each with 2 riflemen and an LMG team, there is a platoon command squad of 3 figures, and 2 2-man "teams" with a 60mm mortar (in the back), and tank hunters (in the foreground).
I have found the pennies to be very robust for game use. They are heavy enough to give a firm placement to the figures, and they provide some measure of protection for the figures.
Been doing it this way since the late 1990s, and it has worked out pretty well for me so far.
Your mileage may vary.
-Mark
(aka: Mk 1)