You have done a very good start. Starting with vanilla js helps you to understand what happens under the hood.

Once you know how the Ajax works you can move on to using frameworks.

Using frameworks always saves time and increases your productivity.

Sticking to vanilla js is not a good idea though execution is much faster compare to using frameworks.

Frameworks takes the responsibility of dealing with different browsers which you need not worry about.

If you asked this five years ago, jQuery would have been the hands-down answer because functionality in general was implemented so differently/poorly/not-at-all across the various browsers (and one really really bad browser in particular).

You will never go wrong with an understanding of vanilla JS. As for jQuery, you will not need jQuery if you get into React. (okay so... I have a React project that includes jQuery because of Semantic UI... but pretend what I said before is true).

Also, what @lichtjaeger said... look at the new 'fetch' functionality.

Learn things the the vanilla JavaScript way using XHR and wrap your head around those concepts and then your good to move ahead with any libraries approach that way you know what they do under the hood...

Instead of JQuery you should use the "fetch" API, that replaced the old XHR solution.

The browser support isn't well yet, but you can use a polyfill service or the stand-alone polyfill.

If you're going to be diving into react, give axios a try

It is generally frowned upon to mix jQuery and React. If you don't know how to do AJAX with jQuery already, feel free to learn it, but it might hold you back a bit if you get too used to it. For people like me who have gotten used to the jQuery way, we're at a bit of a disadvantage. I have to learn how to do it all over again with vanilla JS. I used to do it the vanilla way, but browsers kept changing how they work under the hood, and using jQuery made sense at the time as it handled the nuances behind the scenes. These days, it's not necessary due to browsers finally getting their act together regarding standards. Keep in mind, jQuery AJAX calls are simply function wrappers around vanilla JS. You definitely don't need to do it the jQuery way these days. You could make your own function wrapper to simplify making the calls.