any help would be appreciated
I recently reduced the server wait time on a client website from over 5 seconds to about a third of a second.
What didn't help
Enabling the Joomla cache would probably have helped but this often causes issues for me with CAPTCHA's not working etc.
What did help
Apart from all the usual steps such as reducing the number of third party extensions, finding the fastest third party extensions, enabling GZip etc, there were two things that really helped:
1. Reducing the number of modules that are loaded
There were a few places where I was able to reduce the number of modules I was loading.
For example, I was able to combine several modules in the footer area (social sharing buttons, a footer menu, a copyright notice and developer credit, member signup and login buttons and a logo) into one Custom HTML module.
I used responsive classes supplied with the template so that the columns still worked well responsively.
I was able to use the same trick in another area of the template, reducing three modules into one.
This helped reduce the server wait time by a couple of seconds.
2. Upgraded Hosting
The website was still too slow, so I convinced the client to upgrade their SiteGround "Startup" hosting account to the "GrowBig" account which includes an option to enable dynamic cache.
Once dynamic cache was enabled, the server wait time reduced to under a second.
I am using dynamic cache on all my own websites and quite a few client websites and dynamic cache does not seem to interfere with CAPTCHA's etc or cause any other issues and I am using quite a range of different extensions.
I'm sure there are other improvements that can help but this is what worked for me.