Shaikh Ibn ul-‘Uthaymeen rahimahullah:

“The Scholars have differed: does seeking counsel precede or Istikhaarah? What is correct is that Istikharah comes first. Istikharah precedes due to the statement of the Prophet sallahu alayhi wa salam:

إذا هم أحدكم بالأمر فليصل ركعتين

“When one of you contemplates entering upon an enterprise, let him perform two Rak’ah of optional prayer…”

[Sharh Riyaad us-Saliheen (1/792)]
This is also the fatwa of Shaikh Yahya al-Hajoori hafidhuhallah:

Question:

Which precedes: Istikharah or Istishaarah?

Answer:

Whichever he precedes with, then there is no harm. However, what is more deserving is to precede the Istikharah.

[Source]

Translated by

Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan