35/50 are great little things for the money, one thing to think about when looking and trying to decide based on use is your crop factor, as you have a crop body, your focal length will be x1.5, so in reality, the 50mm will be more like 75mm (50mm x 1.5) 35mm will be 52mm ish. just a little thought as i bought the 50mm for indoor stuff and found it quite long, well longer than I expected, so i ended up trading for a 35mm but the 50 may well work for you, its all personal.
I had an 18-200 and found it more than capable and for around £200 its a nice little lens (well not that little) might be a lens you can do landscape and the odd birdy ? but 200mm is very short for wildlife.
the good thing is you have an 18-55, so play and enjoy then look back and see what sort of focal length you use a lot.