Do Split Squats twice a week for strong legs. Split squats enable you to absolutely hammer the thigh muscles without the low back giving up first (a common problem with back squats). You will also get a great range of motion, as split squats are not inhibited by mobility limitations. What’s more, there are so many split squat variations, that you have lots of options to rotate through. Gradually, target to do with Dumbells, half your bodyweight.
Dont be upright while doing it. If you remain upright, it will overload the back legs. Its a singlet leg exercise and the back leg is only there to stabilise. Start at half kneel position, drop your hip back so that you have a nice angle position of the torso. 80% of the load should be going to the front leg. Ensure that front shin should be roughly above the ankle. Breathe out as you go up. Split squats are great for increasing lower body mobility. They are also great for preventing strength imbalances between the left and right leg.