As you can see in the structure above it all starts from Mercury. Whenever you kill Vor you unlock Mars and Venus. Thereon you have to kill bosses to unlock different planets. It now splits between Mars side and Venus side.
Now lets look on each boss for each planet and what you can get on each mission completion.
Mercury – Vor: Vor can grant you the Cronus Sword blueprint as well as the Seer Pistols Blueprint.
Venus – The Jackal: It can get you parts for Rhyno as well as the Howl of the Kubrow Quest.
Earth – Vay Hek: This one can get you parts for Hydorid; you need to be Level 5 to be able to fight this guy.
Mars – The Sergeant: The Seargeant will give you parts for Mag.
Jupiter – Alad V: Will give you parts for Valkyr.
Saturn – General Sargas Ruk: A big pain for a lot of players once they get to this boss; it will drop however parts for Ember.
Uranus – Tyl Regor: To be able to go to this one you’ll need an Archwing; it will get you pieces for Equinox, in total there are as much as 8 parts.
Neptune – Hyena Pack: This will drop the parts for Loki.
Pluto – Ambulas: This will get you the parts for the Excalibur.
Ceres – Liutenant Lech Kril: Another hard one and it will eventually drop for you the parts for Frost.
Eris – J3-Golem + Mutalist Alad V: Here things are starting to get a bit different. You need to fight Mutalist Alad V to get Mesa and the J3-Golem to get the new warframe Alice. However further details are required: Mutalist Alad V can be fougt by collecting 3 Mutalist Alad V coordinates and the J-3 Golem can ONLY be fought after completing the quest called “The Jordas Precept“.
Sedna – Kela De Thaym: It will get you the necessary parts for the strange, yet effective Serro.
Europa – The Raptor: You can build Nova with parts dropped by this guy.
Phobos – Lieutenant Lech Krill + Captain Vor: It is a dual boss fight, but by completing this one you can get parts for Trinity and Miter which is basically a saw blade gun.
Orokin Derelict – Lephantis: You need to make this key and you need to fight Lephantis which will give the parts for Nekros.
These were the planets order and bosses droppings in Warframe for each of them. Now that you have your plan all you need to do is to go out there and start kicking some asses. Most of them are straightfroward, but others require you to do a bit more. Enjoy and happy framing!