Iguasu Falls and the Grand Canyon and Harbor of Rio De Janeiro and Amazon Rainforest and the Great Barrier Reef Victoria falls and Mount Everest is my list of what I consider to be the most outstanding natural wonders.
I have been to the first three and they were worth every cent for the billion dollar emotional excitement which they provided.
The only remaining place where I would intensely like to go is scuba diving the Great Barrier Reef in my retirement years but I may have to wait a decade before that desire translates into fact.
You probably have a bias toward human made wonders of the world so I have included a Wikipedia article of some other choices which you may like personally.
My suggestion is don’t waste your money on minor excitement and use YouTube and Google Earth to visit your favorite places on your computer.
If you would like to travel to a great natural wonder in person start saving about 5% of your paycheck for that one or two trip to the most exciting experiences which nature can provide. Enjoy!!!!!!