Is it necessary to bind oneself to a group?
No – you are an individual and your personal needs are taken into account.
There are many ways to do Scientology: You can read a book, you can attend a course, you can take auditing sessions. Of course you also can work in a group, but there is no obligation to do so. There is no demand that you become part of some group or organization to be eligible for auditing.
The goal is to become free and causative, and all efforts are subject to this goal.