There is only one thing that is guaranteed to increase penis size - The natural progression of Adolescence into Adulthood when, despite constant claims of 8"+, it grows to an overall average of 6" - 7" - the perfect size designed by evolution & nature in general to serve its purpose. It's a strange thing that it only ever seems to be males that are preoccupied by the size of their penises, more often than not making over exaggerated claims of their size, yet 99% of women who express any size preference at all far prefer the standard 6" - 7" average, and if a size preference exists at all it is one of girth rather than length.
Nothing out there will get you bigger. Nothing. Don't believe all those "boner pill" type ads. They're all bullshit and made for stupid people. Be happy with what you have.