Rickyho, focusing on building a stronger and efficient squat should be your primary concern in the beginning. Once you can squat around 2-2.5 x your bodyweight, I would look at putting in varied squat styles into your training. For thighs, one of my favorite quad builders are narrow stance/heels raised higher rep front squats without any pause b/w reps without accending to full lockout to maintain stress on the thighs. I've had more success from strict from front squats for building my quads than anything else, but you'll have to experiment for yourself of course.
For your hams SLDL/RDLs, glute-ham raises, and even leg curls with bands are great. You can perform the GHR on the ground with your feet anchored, and these are awesome for your hamstrings.
On any given week however, if you are consistenly working your deadlift variations and barbell squat variations you should build a nice pair of legs. The KEY to building bigger legs in my opinion is simply working out like a man with a high pain tolerance. Too many people cut themselves short of about 6 reps on their squats; even when you are breathing heavy, dizzy, and legs burning-- you can always grind out more reps on squats. Generally you can get away with being a pansy on bench, rows, etcetera and still see results, but you HAVE to work the hell out of your legs to significant results. Just my .37 cents.
Edit: Try throwing the front squats in place of regular squats on one or two of your days. It is easier on your lower back and might be a nice change of pace for you.