In Appendix I of 'Light on Yoga' by BKS Iyengar, he outlines a 300-week-long course (6+ years!), at the end of which, one should be able to do all asanas (poses) instructed in his book (200 asanas, in total). The poses for the first week are as follows: tadasana (mountain pose), vrksasana (tree pose), utthita trikonasana (extended triangle pose), utthita parsvakonasana (extended side angle pose), virabhadrasana I & II (warrior I & II), parsvottanasana (intense side stretch pose), salamba sarvangasana (shoulder stand), halasana (plough pose), savasana (corpse pose). Additionally, each pose is assigned a level of difficulty, ranging from 1 to 60.
I always begin my practice with 12 sun salutations: to warm up, to stretch, to get into the yoga mindset. I feel ready to do the routine once I've completed this warm-up. There's nothing too terribly challenging in this first routine. The highest level of difficulty is a six for parsvottanasana. I did have a little trouble maintaining my balance during this pose, so I came out of it, did the other side, and repeated the pose for both sides. I also felt some discomfort on the medial aspect of my wrists. Additionally, one is supposed to place one's chin on the kneecap, which I wasn't able to do. I just don't bend that far yet. :-)
Ideally, I will do this routine daily for the first two weeks of the course. I have looked ahead in the course, and some of the poses that look rather challenging don't have a high level of difficulty assigned to them. I can expect them early on in the course then, but if I start to run into pose after pose which I cannot do correctly, then I may have to pause and work on these poses for a while until I get them.