I just cut my hair and now it's all frizzy, what should I do?

I recently just layered my hair for the first time and now I regret it. My hair use to be sleek and shiny and was never too thick or too thin. Now it is dry and frittle and has become frizzy. It is also too thin because that is what happens when you layer hair. My hair is not as beautiful as it once was and my haircut would look great if my hair was poofy and dry. Some of my co- workers recommended oil sheen to me because they say it will make your hair shiny and not poofy anymore. Does anyone have any recommendations as to what to use in this dilemma to fix your hair?