It usually comes in the first week of the month or sometimes might come just before the month ends depending on prev event although I think the latter only happened once. As for ninja I don't think you can get any for 2k. I think Sage Jir is like 12 points per frag and on average you get around 55-60 points per 10 throw so you can do the math based on his frags if you need him.
Danzo is around 20-25.
Sage Naruto I think is 45 but I don't remember.
Dpb Hidan was something like 60 per frag.
I recall Edo Haku being there for maybe 30 per frag so at 900 points you will be able to get him with 2k