In my opinion, self-made German school cone look better than purchased ones. But still, you need to spend reasonable time and reasonable money on creating a cone. Otherwise, just buy and not rack your brains. In the last week before the Einschulung, ready-made Schultüte are very inexpensive.
German primary school
School cone in Germany (Schultüte). History and list
An obligatory attribute of the first day of school for a first-grader in German-speaking countries is Schultüte (literally “school bag”). In this post about school cone in Germany – its history and what is inside.