For a first time female user at your size, 5mg daily is the standard starting point - low enough to gauge how your body responds before committing to anything higher. Some women do fine at 10mg but there is no reason to start there when you can work up gradually. Run it for 6-8 weeks, watch for virilization signs - voice changes, clitoral enlargement, unusual hair growth. At 5mg the risk is low but it is individual so pay attention.
The loose skin question is worth managing expectations on - anavar will help with muscle hardness and density noticeably, but loose skin is a different problem that compounds do not really solve. BPC-157 and GH peptides you may already know actually do more for skin quality than any oral will.