1. Be a Dunmer, their natural 50% fire resistance cancels out vampirism's weakness to fire. At level 1, you still have an enhanced resistance, at level 2, you have no resistance, but no weakness.
2. Find and activate the Lady Stone, which makes you regenerate your health and stamina 25% faster, negating their lack of regeneration in sunlight.
Also, general vampire discussion/advice/tactics on playing one. And besides enchantments, is there any way to gain a magicka regeneration bonus?