I want to inquire if one can ask someone to do Istikarah prayer for, as I can't figure out the conclusion from it myself.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

The Istikhaarah prayer is a form of worship, and in principle, acts of worship are not carried out on behalf of others unless there is an evidence for doing so, like in the case of Hajj.

The scholars agreed in a consensus that a person is not allowed to perform an obligatory prayer or a supererogatory prayer on behalf of any other person whether the latter is alive or dead.

Ibn Abdul Barr reported this consensus in his book entitled Al-Istidhkaar.

Therefore, if a person wants to carry out any matter and wants to seek the help of Allaah in it to decide for him which matter is better for him, then he should perform the Istikhaarah prayer himself and should not deputize anyone to perform it on his behalf. However, a person may supplicate Allaah for his brother to guide him to the best in his matter.

His supplication will help him, Allaah willing, if the supplication is said when it is most likely to be responded to since supplications made by a Muslim in the absence of his Muslim brother are responded to as mentioned in a sound Hadeeth.

For more benefit on the Istikhaarah prayer, please refer to Fataawa 8530, 90147 and 90291.

Allaah Knows best.