Minimally.
Minimally.
+15
Maybe 13 because you can three chest them easier without the third affix but you need to progress to them simply applying for them all without experience won't work and you need to learn the dungeons
Pretty sure off the top of my head:
2k is basically all 15s 'completed' (still receiving score)
3k is 2 23's, 7 22's, and 7 21's
you can get to 2k without doing every dungeon on a 15. OP I would aim to do them all on a 13, both on Tyrannical and Fortified weeks and see what your rating gets to with that. Then you can pick and choose which dungeon you want to do to hit that 2k; some are easier on Tyrannical, some are easier on Fortified, and some of them will have sucky affixes while you might benefit from getting 3 easy affixes in one week.
If you want to play the lowest/easiest keys possible, I would suggest doing 13s because you only have 1 affix at 13, and so far this season, the first affix was kinda free in every week.
Playing every dungeon on 13 should be enough for 2k, depending on your times. Worst case you can throw in a 14 or two, but it shouldn't take much more than that.