Best and Lowest Compression Method

[Teslock Pro]

I know many of you might be thinking that I shouldn't post this because there is already a thread for "Best Compression Method For Specific Game" but I am not talking about this.

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I need to know the best compression through which I can compress 16gb to like 8gb (half of it). I have seen FitGirl's Mad Max go 3gb from 29gb. (I know this might be because of file types, some files get compressed to their maximum level and some aren't that much compressible). But I run a YouTube channel, and I have to give the best to my audience. I am still searching for best compression methods. I don't understand LZMA, PRECOMP and others. I am a total beginner in this. If anyone from you know that how to highly compress games than I would be thankful to you.

Sorry for bad english.