The first question you need to ask yourself is what sort of army do you want? What do you find most fun?
In my personal experiance there are 4 potential list styles to play with:
1) The Gunboat; Your looking at warriors in raiders, kabalite trueborns with blasters in venoms, ravagers. This play style has taken a hit recently with release of 6th edition but if you fancy raining down copius amounts of firepower this is your list, combine that with the duke and splinter racks and you can have a 1500 point list shooting off 180+ shots a turn
2) The Wych cult; wyches, wyches and more wyches and all in raiders. Everyone with haywire grenades, a haemocules with each squad, maybe Lelith Hesperax or an Archon. This is the army you want if you just want to chop up everything. Reavers are very good in this army and you may want some more anti-tank support. Problem with this is you may lack significant range and struggle if you can't get into an early assault
3) The Coven; Talos, wracks, grotesques etc. If you want a tougher army and a cool looking/theme
4) The Combination; My personal favourite. With this list you can fit a lot of things into 1500/2000 pointsand I find them really competitive, fun and well rounded armys to play with. What you want here is Blasterborns (Trueborns with blasters) in venoms with an extra cannon, maybe 3 squads of Wyches in raiders with Haemocules and maybe an archon for your cc punch. Maybe a squad of warriors to hold down a close objective. Ravagers and a Razorwing for ranged support. Large squads of reavers to contest objectives late game and attack weak flanks.
Some general tips:
Wyches are great. Give them all haywire grenades and you have a fantastic anti tank unit, a 10 women squad can multi-assault a collumn of tanks and wreck all of them in a single assault, always give them haywires!
Nightshields on ravagers and if you can afford it, everything else, these are great at keeping things alive!
Play aggresivly, get wyches into cc as soon as possible and overwhelm your opponant, If you can attack half his army with your whole army do it, play unfair!
Delicious and Coven-Baked for your Pleasure
A very slow, 30K Salamander Distraction Log: VULKAN LIVES