I've found that spamming 3 R gatcha tickets will hit the minimum to get the SR. That's how I got the limited SR in the previous Nest. If you fail to get the SR you'll usually receive a SR5 but there's a good chance to receive 1-2 consumables instead.

If you're not interested in investing so much, then spamming 1 R gatcha ticket will yield the best results overall. Most of the time you will get SR3's and sometimes SR1's/R's. Eventually you'll get the N and R.

Results may vary but this is from my experience.