Friendship is the most important, non-commitment bond that people experience.
Right at the beginning of a friendship, it is important that you have experiences together that you can build upon. It is only by doing so that you can work out whether you are compatible as friends. The importance of mutual experiences cannot be overestimated.
Joint experiences – regardless of whether they're good or bad – give you a sense of camaraderie. They create memories and give you a sense of having things in common. These are precisely the things you can use to establish friendships. The individual feels stronger when they are in a group. It helps to minimise inhibitions and fears if the person shares them with others.
Perhaps especially because they are random acquaintances that you are making. The history of friendship shows that friendships that aren't initiated by third parties, but instead happen by chance, are often the most intense. A connection that was originally intended just to save money can grow into a camaraderie that lasts a lifetime.
I recommend simply taking a trip with a rowing boat on a local lake. In these 20 or 30 minutes you have to be in very close proximity and have to coordinate with one another. It is associated with a certain dynamic which means that after the trip, you can say with a relatively high degree of certainty whether you want to spend a long period of time with this person.