I think with anything you will get ads while on a site. What you will not get is tracking with the DDG. No more looking at lawn tractors and then getting bombarded with advertisements for lawn tractors, or at least cut it way down. That has been my experience.
You just want to hamper them from making a profile of you and using that profile to manipulate you, because that is exactly what they are trying to do. They can end up knowing you better than your own family does, or perhaps even better than you know yourself. That is the goal for them. And, of course the ultimate goal is money, money, money.
There is a documentary that I believe is on Netflix now, the name eludes me, that really shows you what they are doing. They have some of the people that created all this that are now feeling guilty about it and are speaking out.
If you are heavy into the big social media sites then they got the profile made. And, there is no way to be completely out of it unless you stay completely offline, but you can really reduce it.
I am certainly not claiming to be an expert on any of this. I do not even like the word expert for that matter. However, they are about as close to being experts on what they are trying to do as you can get.