A 50mm lens is a 50mm lens whether you put it on a DX or FX body!
What sets the two apart is, on an DX body you get the equivalent of a 75mm lens compared to the same lens on a FX body.
As an example, take a picture with the FX body and 50mm lens, then from the same spot take the same picture with a DX body and the 50mm lens. What you get is a 'more zoomed/less wide/cropped' picture from the later.
Now here's the most important thing for me... Am I likely to go to FX in the future anytime?
Yes, then consider which lenses you buy now as DX lenses won't work (and that's a very loose term) fully on an FX body.
No, then buy any lens that suits your needs as a FX lens will work on a DX body with no loss of quality (some may argue you get even better IQ with a FX lens on a DX body, but that's a different story all together)
Remember, the "equivalent focal length" is only relative - so if you are never going to use FX or 35mm, then on your DX body for all intents and purposes, it doesn't matter about the "crop factor"
What sets the two apart is, on an DX body you get the equivalent of a 75mm lens compared to the same lens on a FX body.
As an example, take a picture with the FX body and 50mm lens, then from the same spot take the same picture with a DX body and the 50mm lens. What you get is a 'more zoomed/less wide/cropped' picture from the later.
Now here's the most important thing for me... Am I likely to go to FX in the future anytime?
Yes, then consider which lenses you buy now as DX lenses won't work (and that's a very loose term) fully on an FX body.
No, then buy any lens that suits your needs as a FX lens will work on a DX body with no loss of quality (some may argue you get even better IQ with a FX lens on a DX body, but that's a different story all together)
Remember, the "equivalent focal length" is only relative - so if you are never going to use FX or 35mm, then on your DX body for all intents and purposes, it doesn't matter about the "crop factor"