I know what your thinking plugins to speed wordpress, isn’t that just adding to the bloat. These plugins do work on the database and files in order for your servers to have an easier time serving the data to your viewer.
There are a few plugins that can optimize images I do have my own favorite. Its a one click and done solution. I can simply click on the unoptimzed media tab in my backend and select specific images to optimize, or I can do them all at once with the bulk optimize option.
This is my first step toward speed demon status with my wordpress installations. Images can be one of the largest factors in page speed if they’re not optimized. I also generally will go in and crop the size of the images I am using with the media editor as well. There is not much need to be serving a 3000 x 1400 px image unless your running a photo sharing or sales site. My favorite plugin for this is EWWW Image Optimizer, for its quick easy use and quality optimization.
There are plenty caching plugins but some work better than others. I’ve found that for my money ($0), I find W3 Total Cache top notch. This plugin raised my GtMetrix score by about 5 points for both measurements (PageSpeed, andYslow). It also helped get my load time under 2 seconds, loading in nearly 1 second for most checks. This was quite an improvement and almost halved my load time (which already was showing fast according to their rating system).
The last bit is to optimize the database. If your doing regular updates to the site and need to access revisions you may want to wait until your latest post is finalized before running this. It cleans out the multiple revisions that are created each time you save a draft or make a new edit to your post.
It removes spam comments and will clean up auto drafts, as well as posts in trash. I’m not sure how much the improvement was when I implemented this in my own site. I do know it helped shave 2 seconds off one of the slower sites I have used it on.