Bonjour et bienvenue Blackyell.
Families are useful, but you can very much make games without them.
In my tutorials, I tend to make projects under 100 events and being "friend-edition" friendly.
So I don't use families in them.
In my personal/pro projects, I use them when it feels it can really lighten the code/it makes sense.
To me, the real plus of the families is a facility in code writing and possibly an "OOP" way of dealing with objects.
You can set common behaviors/instance variables that will be common to all the object types in your family but also add specific behaviors/instance variables to the object types of your choice, and be able to do a "first pick" on the family before refining to the specific object type and then using its own behavior/instance variables.
I hope this helps you visualizing a bit better what families could bring to you.
I strongly support the idea of buying a license, as even the personal one will really help you to fully test and learn all the subtleties of C2.
Nevertheless, to learn the basics and make your first experiments/released little games, the free version is really more than enough as it is.
It's soon Christmas, it's worth asking the license as a gift that will provide hours of fun if you're into game making rather than "straight programming".