50 is reasonable 100 not so much, given the current market situation for darkroom stuff. Value-wise, it's a good deal either way.
An under-lens multigrade filter kit comes with a holder, or you can use the larger gel filters in the filter box.
As stated, you will probably want a better lens, and a 50 mm would be a little better for 35 anyway. But this will get your feet wet, and gets you most of what you need.