In 11 years of playing this game i can offer two pieces of advice:
1. enjoy your time and the people you interact with.
2. don't get attached to pixels and definitely don't define yourself by achievements and/or loot.
Cheers.
16 slot bags are super cheap (5-10g on most servers). Bank bag slots are 25g each.
It's sufficient space for most toons. That said, pack-hoarders will never have enough bag-space.