To be able to obtain the Ignis Wraith you have two options. The first one is to trade with other Tenno to obtain the Ignis Wraith Blueprint. The price of this weapon varies a lot, and it will not depend on your trading skills, because it depends on finding a Tenno who do not want to speculate with its price.
The second one is to be member of a Clan that got the Ignis Wraith Blueprint in the “Operation: The Pacifism Defect” event. In this case, you only have to buy the blueprint and craft it in your foundry. Remember that you have to obtain the required resources previously.