If you are having trouble finding a friend to complete the quest with you and don’t have anyone to help you in multiplayer, you can often put a request in the OSRS SOA chat channel, or answer one, as that channel is exclusively for people looking for a partner for the quest. Whichever gain you and your partner choose to join doesn’t really matter, as both gangs generally have the same playstyle and results either way. All that really changes are the tasks you complete and the gear you get at the end, which is rapidly outclassed by better gear anyway the further you get into the game. Then you can talk to your newfound friend in the chat and work together to complete your objective, whether that is getting half a shield each or getting two candlesticks. Most players are pretty nice and willing to work together and talk about their gang choices because at the end of the day they are all looking for partners.