Loaded question... lots of mistakes made or Lessons Learned as I prefer to call them! Not sure which to list here, but here are some...
It seems most of us reading this forum have made the same mistakes. I agree with money as it is always an issue. Here are some other mistakes I have made or as they have been called lessons learned. BTW, I have been in business six months and have yet to turn a profit, so I am definitely learning as I go.
1. Not realizing how much money it took to get started.
2. Expecting instant success. Afterall, everyone buys on the Internet and eBay.
3. Did not plan far enough ahead and did not effectively anticipate potential problems.
4. Finding a good supply of vendors, including dropshippers.