What has you opposed to joining a guild?
The answer really is to make friends you can ask to run content with you or by joining a guild.
Best bet without a guild would be doing group finder / dungeon finder and being really chatty, even suggesting to run more dungeons. Send appreciation to good players and send a friend request. If they accept, make note of who they are and follow up later. It’s worked a few times but usually things end at the follow up stage (neither of us message each other ever again xD).

