Welcome to the Dark Kin! You have picked an awesome, and very stylish, army to pick up. The disadvantage is that they can be a bit tough to use well, because they are so fragile. I recommend having a look through some of the tactics and army list threads to get an idea of how people use them effectively, but here are my thoughts, for what it's worth...
DE are a glass hammer army. Live by your manouvrability, strike fast, strike hard and try to use overwhelming force on isolated sections of your opponents line. With that in mind, I would suggest getting some more transports. Although some people do use static warrior blobs, they are very fragile, and Wyches on foot are even worse. As has been mentioned, some people like to play Venom spam, but I reckon a balanced mix of Raiders and Venoms is more fun to collect and play.
Also, invest in some Heavy Support. Ravagers are great value for points, and the easiest to use well, but all of our HS choices have real potential.
Congrats at picking up a great starter force for such a good price. Let us know how you fare with it.