This week is the perfect week to start the Eris weekly missions. There are 3. Do the Shadowkeep starting mission called "A Mysterious Disturbance" and then get the weekly bounty from her that says to go into the lost sectors of K1 Logistics, K1 Crew Quarters, and K1 Communion (to get the key thing for access to the vault in the 4th lost sector). Once that is done you go to K1 Revelation and complete it then go into the vault area which gives you the Quest for Sai Mota. Once you have that you go to Altars of Sorrow to defeat Nightmares with arc abilities. Then you go back to Sanctuary area on Moon and then through the portal to visit Eris in the Abyss overlooking the triangle ship. That completes the first week. It will also give you another quest, but that is for the exotic rocket launcher, which if you already have you can just vault that quest.