Workout Routines?

Hey everyone!! Before we get started I want to tell you a little bit about myself :) I'm 15, 5'7 and I weigh 149 lbs. In the past couple of months I've noticed that I've been steadily gaining weight :(( Right now, I'm pretty disatisfied with how my body looks and I want to fix it but I don't know where to start! I want to tone my stomach and strengthen my core as well as tone my thighs and calves. Can any of you girls recommend workout exercises or a workout routine so I can get started?? Thanks <3