I would suggest waiting until after you've completed the crucible stage of your first exotic sword quest before fully upgrading and infusing the other legendary sword types as you then should be able to skip the crucible portion on the other two exotic sword types. You will be able to get all 3 on one character. I purchased the other two legendary swords and infused/upgraded after I did the Guardian kills and planetary materials stages on my first one and then was able to get all 3 quests on the same character - this should enable you to skip the crucible kills for the other two. You will still need to gather materials for all three though. There are some good guides out there if you search for them.