From: Hoorn (NED).
Actually, land units are the *last* thing I would buy with the Free French. The first thing I would buy are naval transports, and particularly AMPHs. A couple of Free French AMPHs, plus some surface ships for escorts, and the Allies can launch an invasion with the US or CW taking a land. After that, the next thing would bombers, for ground strikes. There are never enough air actions; use the French ones.
Land offensives take a lot of units; building at a rate of one unit a turn, you won't get enough land units to make a difference, and even if you got some, they almost certainly would be mixed up with other Allied units, so would not be useful unless those units could move, and if they can move, why do you need the French? The one exception is the possibility of combining with French partisans, but I have never been able to pull that off.
So AMPHs, bombers, and TRSs are the way I would go with the French.
Don't forget the air transports for the Para's. I like to have at least one of those for Free France too. And you are right for not building a lot of land units with the Free French. But in this game, I would have build one since that partisan is in Bordeaux...