Before you decide to get the 50mm 1.4 lens you may want to borrow/rent it. I've heard from several people that the 1.4 is really hard to get spot on for the focus (both eyes in focus) and they usually end up upping it to 1.8 anyway. The 1.4 would allow you to shoot in less light but requires more technical skill. Which is why I chose the 1.8 in the first place.
Lenses are so personal and dependent on your skills, your needs and just your personal preferences.
For me I thought having the 50mm lens looked silly on my big old camera and love the weight of my 18-50mm lens, but others find it heavy. So see it is all subjective. Oh and I bet if you shopped, you could find a used 50mm lens, a lot of people start with it and then change. Just make sure they protected it from scratches. I've bought two used lenses and have been very happy. I could talk lenses all day!
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