I can't remember my first tour. It was about 40 years ago. I remember my first few tours, I just can't remember which was actually "the first". However, I remember the feelings during and after. I loved it so much that I'm still loving it 40 years later!
I've made my share of mistakes in what to bring too. I've compiled a checklist that I've refined over the years. If I actually use it and carefully check things off as I pack them, I do pretty well. I take notes while on tour as to what to bring and what I could have left at home.
I'm a fan of gears - the wider range, the better. I like a 3 x 9 for touring, with at least a 24-tooth granny, and the biggest cog in back I can fit.
I don't "get" the single speed thing or why someone would want to minimize their gear selection on tour. But I'm old. You go, friend!