Hi guapo. Instead of considering lenses, why not consider flash guns and lighting kits? Lights are important for portraitures, especially indoors. Also consider a reflector as well for outdoor shoots. With the price of an AF-S 35mm f1.8, you can get a decent lighting kit that includes 1 umbrella kit, 1 softbox kit and reflectors. Or a flash gun, maybe SB-600 new or SB-700 for alittle more top up. The 18-55mm is a great lens, it is sharp and it gives you nice bokeh.
Check this out, i have made a thread that you can capture stunning photos with a kit lens, the 18-55mm.
http://www.clubsnap.com/forums/threads/878197-How-shallow-does-the-DOF-of-the-18-55mm-produce