You only need Vanguard marks to buy the helmet and the chest pieces of your armor. Or weapons. Boots and gloves only require marks, which is really nice. With an exotic, you only need a single level (assuming you're already level 3, that is) to purchase the gear you need.
And, after saying I was going to wait, when I got home I saw 4 friends online during the middle of the day, so I went ahead and spent the $35 for both expansions.
Also, the Vanguard scout rifles look really good. =( Better than this Juju I just popped and leveled. Don't have enough marks though. =(