Is it ok if I make a video which is a screen recording of me doing different google image searches and putting it on youtube with ads enabled?
It's only fair use if it follows the FAIR use act. See this advise from Stanford
Essentially, as long as you are showing the images either for the purpose of criticism (e.g. "All the images produced of 'Insert Sporting Mascot here' are taken in really awful lighting, as you can see on these images") or you are using it for the purposes of parody (e.g. "My mate really looks like 'insert famous person here', see [proceed to show the picture]") then you should be okay.
An important distinction however is that your body of work must be directly related and benefit from the citisism/parody. You can't just be doing a gaming video and randomly put a well known celebrity in the thumbnail, then at the end of your video have two seconds where you go 'And now a review of Kanye West. I don't like his shirt in this picture. Finished' in order to justify their inclusion. However, if you spent 10 minutes making jokes about Kanye West in relation to the game you're playing, then you should be fine.
Nope. The main problem is that posting a picture of a picture is a form of copying, and you need permission of the copyright holder to copy their stuff (this is embodied as a Youtube TOS clause, number 6D, in addition to being a copyright violation). That is especially true if you copy stuff to make a buck. That's for an ordinary image search. It may be possible to find (and thus copy) only images that are free from copyright restrictions (either government works or publicly licensed images); you'd have to make sure that the images are licensed for commercial exploitation (lots of images are NC-licensed).
The real question is, what else are you doing? I think (IANAL, do your own research) that it might satisfy fair use if you're doing something else like commentary, etc., etc. I am not 100% sure of this.
I don't think posting a picture of Google Image Search results in aggregate is the same as posting any single image anyway - that definitely looks more like a transformative work ala collages.
TL;DR Go read the longform, but there are some cases when it's okay to do that. I'm just not certain this is one of them necessarily.