First off welcome to the Dark Kin! I would first suggest reading through the codex throughly and figuring out what exactly you want to do. DE have many styles of armies, and find what kicks your fancy and start looking on how to fit that theme into your list.
Secondly I would get a base army together. For beginners I normally suggest the patented SR beginnger 150 pt list. Its like this
150-Archon w/ Huskblade, Soultrap, Shadowfield, Combat Drugs, Haywires
223- 9 Wyches w/ Haywires, 1 Shardnet, Hekatrix w/ Agoniser; Raider w/ Flickerfields, Shock Prow
245- 10 Wyches w/ Haywires, 2 WW (so shardnet, gauntlets, or flails, your personal preference) Hekatrix w/ Agoniser; Raider w/ Flickerfields, Shock Prow
190- 10 Warriors w/ Splinter Cannon, Blaster; Raider w/ Flickerfields, Shock Prow
190- 10 Warriors w/ Splinter Cannon, Blaster; Raider w/ Flickerfields, Shock Prow
78- 3 Reavers w/ Heat Lance
78- 3 Reavers w/ Heat Lance
115- Ravager w/ Flickerfields
115- Ravager w/ Flickerfields
115- Ravager w/ Flickerfields
Total- 1499 pts
The makeup of this is 2 Battleforces, 2 Raider, 3 Ravagers, and an Archon Blister (but it seems you already have the 2 battleforces, so all you need is the extra vehicles) Its a cheap army for its size, shows the strengths of DE, and is pretty competitive to boot (its not optimize by far, but gives you alot of options). Its also a great template to build apon to fit your style of play more.
From there I would take what theme you like, and try to incorperate it into this army. Like wracks and haemies? Maybe drop a wych squad and the Archon add a nice size wrack squad with a cheap hamie leading it. Like Hellions, well again drop a wych squad and the Archon, and add Baron and nice sided hellion squad. the oppotunities are endless!
Once you have the theme you want, then I would start pushing towards 2k and continue to fill out your themes. Need more AT? Trueborn are good for that. More troops (always take most troops you can) a few 5 man warrior squads in venoms will do the trick. DE have a ton of options and they are up to you to decide what to get into.