Depending on your setup, it may be a challenge to get your site working fast enough when you post lots of media. I've experienced themes before that didn't respond well to multiple embedded Youtube videos, for example. But if your site is heavy on the images, you'll definitely want to look at ThemeIsle's advice.
Image via Pixabay
The blog recently published a guide on how to optimise your images before they hit the CMS, so they'll be processed in the ideal way after they're uploaded. Things like cropping, which file format to use, sizes, and quality differences. Did you know lowering the quality of an image to 80% is pretty much unnoticeable? The same rule applies to video -- when transcoding in apps like MPEG Streamclip, lowering the quality to 80% speeds up your job and the viewer won't be the wiser. It's only after repeated downloads and uploads that an image really starts to lose its fidelity.
Another good takeaway, which the post offers a good free tool for, is "lazy loading":
Images at the top of the page are prioritized, while images below the fold are loaded only when the visitor scrolls down the page. This makes lazy loading the “just in time” equivalent of web page loading.
Some of the tips involve costs, such as the Jetpack service Wordpress offers with each install, but mostly these are tips that won't cost you. In fact, while Photoshop will set you back some cash, I'd recommend Paint.net for simple editing of blog images. It's lightweight, quick to load and close, free, has lots of available plugins, and unless you're doing serious graphics work, it has everything you need for making your images sing on a blog.