One home truth before I get started: $150 as a lens budget could actually mean that a dSLR is not a great choice for you, because equipping yourself with a dSLR system is expensive. While a camera body can easily be picked up in the $300-$500 range, to get a good basic system is more in the $1000-$2000 range. If $100 one way or the other is going to break the bank, you may want to consider a fixed-lens camera, instead. These days, some of them even come with APS-C sensors.
If you're seriously into photography and using a crop-body, neither of these lenses is likely to be the tool of choice for you, because they are consumer grade lenses--good, but not fantastic and there's undoubtedly a better lens out there for the specific thing you want to shoot. The problem is that as a beginner, you're caught in a chicken-and-the-egg dilemma. To know what lens you want, you need experience enough to know what lens you want.
"Body only" packages aren't really for a newb to order up their ideal system à la carte, but for someone who already has all their glass not to be lumbered with another 18-55 kit lens when they upgrade bodies.
18-55 kit lens
The reason the camera comes with a cheap, consumer-grade 18-55 lens, however, is so that you have something to shoot with out of the box, and you can get experience. It's also not a horrible terrible lens that will turn all your images butt-ugly just from being used. It is limited. It has shortcomings. There are a lot better lenses out there. But it delivers well enough that you should be able to distinguish between good and bad technique while using it. And, if bundled with the body, it's cheap.
But most importantly, its focal length range covers wide angle to short telephoto, so it's a good versatile walkaround lens that covers the typical vacation, landscape, and daylight portrait shots non-photographers buy a camera for. Learn to light, and you can do crazy good things even with an 18-55 for portrait work. And if you amass a number of photos with it you can begin to see where you like to work in terms of focal length, so you can determine the appropriate prime lenses if you want a low-cost wide-aperture lens.
50mm f/1.8 lens
The 50/1.8 used to be the kit lens on film SLRs. It's also very cheap. But unlike an 18-55, it doesn't zoom, will be a lot faster, and probably optically superior to an 18-55. It probably won't be stabilized and may not have a focus motor, if you're really bargain hunting. And to top it all off, on a crop sensor, its field of view is narrower than "normal", so its use as a general-purpose walkaround lens is far more limited.
It could be a better portrait lens than the 18-55, if you prefer doing natural light or using a thin depth of field. And you can shoot landscapes with it, albeit with a limited FoV. It's certainly nicer in terms of how wide you can open the aperture--an 18-55 lens is typically limited to f/5.6 or smaller by the time you get to 55mm. But the fixed framing can be very inconvenient, especially if you can't move around, or are shooting in tight spaces.
And here's the thing. Roughly the same amount of money could also get you a 35/1.8, and quite a bit more can get you an 85/1.8. And the 35/1.8 would be better as a walkaround, and the 85/1.8 might be better for portraits. And there you'd be, with an almost-but-not-quite-fits 50mm for your money. Chicken and the egg. To really know if the 50/1.8 is the lens you need, a little more experience is invaluable.
