Deimos

If you did not chose Volt as your starter warfame, replicate all of his blueprints from the clan dojo Tenno lab now and farm his resources to build him.
Do the quest “Heart OF Deimos”. This quest will be a long quest that will take bit of time, so settle in for a long ride. You will get the Lanzo Fishing Spear, Xaku Warframe blueprint, and all the blueprints for a Voidrig.
Farm all of Xaku from the Deimos bounties.
Buy the main Nekros blueprint from the market with credits, then farm all of Nekros from Magnacidium.
Visit Otak in the Necralisk, to buy all of Citrine. Farm all of Citrine from MARS/Tyana Pass.

Go to Phobos.