I’ve only been in the hobby for a little over a year now, and at this point my advice would be:
1. Be patient and make changes slooooowwwwly. Any change - adding supplements, adding fish, adding corals.
2. Do your research, then do some more. Spend time on the forums.
3. Try to understand water chemistry.
4. Test your water regularly and maintain a journal.
5. Buy the best equipment you can afford, even if that means having to defer the livestock purchases.
6. Stability. Additional equipment such as ATO units and dosing pumps will help with this.
7. The amount of time you take to maintain your tank will reduce as it matures. Additional investment in the right technology will also reduce this.
I spent a couple of hundred hours on the forums before I bought and setup my tank and many, many hundreds of hours ever since reading more and learning about my tank. We all make mistakes, but research is what ensures we learn from them and don’t simply repeat them.
It’s nowhere near as beautiful as some of the other tanks posted (yet!) but here is my effort so far.