Please Note: Different plugins are more appropriate for different websites. These are ordered as my personal favourite.
If there is one single tool I would tell people to buy for WordPress, it would be Elementor Page Builder. I have used WordPress for over 10 years and I have not come across anything like it. Sure, there are other page builders but this is the first one that I felt like I had full control over my designs and expression combined with a huge amount of functionality.
This single tool has made me more revenue than any other by saving me massive amounts of time creating websites for myself and clients. Elementor is a must-have in my opinion for beginners or advanced users.