I've read a lot of online articles that say a must-have lens is a fast 50mm. Knowing that the 50mm will have a cropped field of view on an APS-C camera, would a 35mm be a better choice?
Only you can decide which is better for you. Don't believe articles that tell you what you "must have." I have a 50mm f/1.8 and I never use it. It just isn't an interesting or useful focal length for me. Someone else may love that focal length, though. Neither of us is wrong.
My advice is to buy a lens to solve a problem that you've already experienced. If you can say "I can't do XYZ without this lens" or "I could do XYZ better if I had that lens", then you have a good basis for making a sound buying decision.
For example, I recently bought a Nikon 85mm f/1.4mm lens, despite the fact that I already had that focal length covered with my 70-200mm zoom.
I bought it because this lens has a spectacular bokeh and very shallow depth of field. The 70-200 also has a nice bokeh to it, but not as much at 85mm as it does at 200mm. Considering this lens usually goes for about $1700, that's a lot of money to pay for a feature. So one should definitely know what they expect when spending money on a lens.
Also, you need to know what the lens doesn't do for you. Going back to the 85mm, I discovered that its minimum focusing distance is about 4-5 feet, so I can't get real close to a small object and fill the frame. It wasn't designed for that. To get the composition I wanted, I had to crop out most of the photo in post.