Wow – you’re starting off at a way higher dose than I did! I started on 20 mg Vyvanse and moved up to 30 after three months, then to 40 just recently.
Even so, I was super-buzzy on the first day of the medication. I was all blissed out in the morning, then at mid-day I felt a little too revved up. (I’d exercised, so that probably contributed to the pounding heart!) By the second or third day the buzzy feeling calmed down, but the improved focus was still there.
I never skip breakfast; I’m a cereal junkie 
so I haven’t got any personal empty-stomach experience to compare, but I’m sure eating something would help! In fact, my doctor’s kind of amazed because I actually gained 3 or 4 pounds since starting the meds. Obviously they’re not dulling my appetite any!