Personally choose one sARM you have researched thoroughly.
S4 is something I'd never use because of the metabolite I've written about In detail
S23 for me was not something I'd suggest for a first run with sarms.
lgd4033 or 3033 is a low dose sARM with a lot of punch.
Remember you will need ancillaries during your run
And proper Pct
I believe this board supports need2guard as a good choice to protect your health while running anything that adds strain.