Guild wars gold is worth buying. Keep in mind that part of the beauty of Guild Wars is finding play styles that suit you. There is no uber class combination or attribute distribution that you need to go into in order to be worth something as a player. Decide what skills you are best with and what skills work well together, and always be ready to experiment.
Make sure you have got some points in soul reaping, because all the weak creatures are going to keep you supplied with energy as they continue to die. The greatest dangers in PvE are facing too many opponents at once, and while experienced rangers in your party will try to prevent that from happening by luring a few enemies towards your group at a time, in the case of a battle against too many enemies, your teammates might find their reserves running dry while you continue to have plenty of energy. In worst case scenarios like that, you will be glad you have it.
Death necromancers will find that the large numbers of corpses are even more important for making their minions with. For much of the game, you will only have bone horrors to choose from, but when you get the spells animate bone fiend and animate bone minions, you have got to decide which suits you best. Horrors only require 15 energy to animate compared to the 25 needed for minions or fiends, so if you are more concerned with using the energy on other skills, you may want to go with horrors or not raise the undead at all. If you want to focus on having your army be powerful and long-lasting, I had recommend fiends, which seem to be more powerful than the other types and attack at range.