For the 1st step, you don´t need people with the quest. You can go alone to any social space and click over the square. You need to play the required activities (Nightfall, etc.) with a fireteam with 3 different classes. They don´t need have the quest. Some steps will require a 3 fireteam in the same step, or people who advanced past the step or finished the quest. These people need to get a replica of the SIVA engine with Shiro-4, in order to help you. The part where you need to kill 3 bosses in WotM, you can kill the same boss 3 times, no need to kill 3 different ones.