First chance you get to become a Vampire lord is after the quest Awakening. When you take Serana to her father Harkon. Harkon will offer you the gift of becoming a Vampire lord. If you take the Dawnguard route instead Serana has the ability to make you a vampire lord instead. She can change you infinitely.
The only perk I can recommend getting as soon as possible is unearthly will as it will increase the amount of times you can you the area drain attack before having to recharge. Do not have an ally with you while you do this as you need to be the killer, also save the perk night cloak for last as the bats will steal kills.