I got the 50mm f/1.8 as a cheap portrait lens; at 80mm equiv it is a fairly nice length. I also use the 100mm f/2.8 macro but that needs a bit more space.
The long end of you 18-55 will be fine. You don't have a fast aperture with it, and its sharpness encourages stopping down to f/8. This is still workable to get an oof background (but a lot harder than shooting with a faster lens) if you considered your subject placement relative to the background.
The 50mm f/1.8 is cheap and optically quite good. It's a pretty good lens for the price. You can shoot with anything though; plenty of people use 24/35mm for environmental portraits on FF. It's all to do with the style you want to develop.