How Should I Make Pikmin-Like Grouping?

If you have ever played pikmin, you would know how the grouping works and how the pikmin follow you around in a group. I would like to recreate something similar without having much fps drop issues. I tried to recreate it by making them keep walking to a circle then stopping if they are in, and the fps dropped by a lot because they form the circle by walking into each other until the circle is formed. Im not asking you to write me any scripts I just want a highlight on how it should be done.