weapon enchant for melee class

I'm currently rolling a rogue and it's about to hit level 50. As a
melee class, which weapon enchant is best suited? Lifestealing?
Crusader? Or +15 agility? Currently I am sword specced. So, if I
were to get a hold of an assassination blade and heartseeker, which of
the 3 enchants would give the most value for the gold spent on getting
the enchantments.

Just wondering so I can start saving/farming for the the gold or mats
needed.