Adverts in blog posts

I have created a simple blog website using Generatepress theme. I was originally asked to put some adverts in the widget area. The adds were basically 300×300 images with links. Easy to do just adding them as image widgets.

Ive now been tasked with putting them into some of the blog articles. Which ive been doing manually whilst making the blog post.

Its struck me that im probably making it harder than it should be and that theres a plugin for that.

So what i want is a plugin that will randomly place my advert images into my blog posts, say afer the third paragraph but randomly from one of my adds. Thers only 3 different adds at present.

Should i just comtinue to do it manually or a plugin.
Which plugin is the most simple, as im not talking paid adds or adsense here, just fixed images with links.

thanks