Death is the most sustainable school in the game. More than any other class, death does NOT need a secondary school out of the main 7. DON'T get any life spells that are not quest rewards, save your training points for the sun damage boosting spells, and make sure to use ONLY life sap spells (whenever possible). With death and the sun school enhancements, they boost 2/3 to the damage and 1/3 to the healing. Life sap spells do NOT boost fully, so be prepared for it
If you plan to play casually and just see how you like Wizard101, start a fire character. You'll go farther, faster. While fun, death is more of a time commitment.
However, if you plan on playing very seriously and taking this game to the limit, start two different accounts (not just two different wizards on the same account), and create a fire on one and a death on the other. Then you can be both at the same time.
Yes, I have both characters. Death is great for soloing and healing while fire is great for those high damage spells ESPECIALLY for AOE damage. However, it has been suggested that balance spells especially humongfrog does a better job for AOE. Check out both. However, I don't think you can go wrong with either class.
For one thing, never, ever combine schools. I would only bother training Death to Feint, Life to Satyr, and ice to Tower Shield. I am an exalted Necromancer, and I really love Death; drains can heal me up and kill the minion for soloing. You also get Dark Pact and Feint, as well as Plague and Virulent Plague, for support.