You'll come out of Hyperspace in a large dust cloud which will hide you from Vaygr sensors. The Oracle Dig Site will be marked by Fleet Intelligence, who will say you need to dock a Marine Frigate with the site in order to retrieve the Oracle.
Start off by conducting all the research you can; you will get a lot of RUs from the end of the previous mission. You may also want to invest in another Carrier and spend the RUs to kit it out fully. You will also get Ion Frigates available from now on; these are anti-Frigate and anti-Capital ships, so use them accordingly. You should construct until you have at least:
Then, ignore your Carriers and Mothership and move all these around to the Dig Site. When you get there, destroy all the Gun Platforms and immediately send all of your Marine Frigates to the Dig Site; the mission ends the moment they dock with it, so they only need to survive long enough to get there for the mission to be a success. The rest of the fleet is for dealing with anything that tries to attack them. In a lot of cases a full-out attack on the Vaygr here will pretty much always result in defeat purely because of the amount and rate that the Vaygr will spam ships at you. The Vaygr numerically outnumber you in every circumstance in this game, so get used to it.
As a result, get a Marine Frigate to the Dig Site as soon as possible, and you can end the mission before you lose all your ships.