Help with working out and getting fit?

Hi everyone I want to get into a routine when I can do something easy and simple with all that I have going on. I go to school full time as well as work full time and have kids. My question is does anybody have anything that will help me to tighten my entire body. I've been doing some things for a week like treadmill/crunches/squats is this good or do I need to improve? Thanks for all that help!
Updates
+1 y
I should have said I'm 115 pounds I just want to tighten my body not lose any weight. I eat extremely well but dieting doesn't tighten.
Help with working out and getting fit?
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