Based on my experience while I was just getting into poker, I made some mistakes as a newbie. It's okay to make mistakes because it's part of the journey to becoming a pro. Learning from your mistakes makes a big difference.
As a new bird, avoid the following costly mistakes:
1) Don't chase losses.
2) Don't play with many hands.
3). Avoid overbetting or underbetting.
These few steps will get you started on a better note if you're new to poker.