best exercise for fat jiggly legs ?

The very best exercises for jiggly legs are cardio and resistance exercise coupled to a sound food intake program.
Works 100% of the time.

^ ding ding ding.

I have some Shape Ups and they help.

Sketchers got sued over these being bogus and had to pay $40 million. I never tried them, but just saying. Might have been some other part of her program that helped her legs, or she may have been one of the 14 people they did work for. Upside is you can probably buy them pretty cheaply these days, if you want to risk it (while wearing really ugly shoes).

Myself, I'm still working on my ugly, jiggly thighs. I will say that my cankles are much improved after several months of daily cardio and weight training. I don't have pictures, but my cellulite used to keep me from wearing shorts (came all the way down to my knees), but now I almost like my knees and I can wear shorts that AREN'T old-lady shorts out in public without feeling like everyone's turning away to quell their nausea. That means that my cellulite has retreated up to my mid-thigh! Also, the jiggle on my calves has all but disappeared. I have to squeeze them to find the lumpiness now, where it used to be apparent when I was just standing around.

Specifically, I do at least an hour of exercise EVERY day, keep consistent with my calorie intake (1200 NET calories -- eating back exercise calories), try to avoid alcohol (that's the tough one for me) and log everything. I started with step Jazzercise (this program incorporates weights and resistance along with regular step moves) 4 days a week and walking 3 days. Over time I've added on to that -- I now do some sort of HARD class at my gym that uses weights and resistance 5 times a week, hike on hills for a couple of hours once a week, do one day of intense cardio on machines at the gym (I switch that up, since it gets so boring -- 10 to 20 minutes on one, then switch to another, etc.), and walk the doggies for around half an hour every day. Someone else mentioned rollerblading, which worked wonders for me in my 30's, when I lived in San Francisco and would skate with my then boyfriend (married now for 15 years) along the Bay. My BFF called rollerblading the "anti-gravity butt lifter" -- really great.

Oh, and I'm pushing 50 here. You look pretty young in your picture. If an old lady like me can do it, so can you!

If you have cankles that is usually not fat, it's water retention. Reduce your salt intake and watch your cankles disappear!

Obviously your diet. Start there. Look at your intake; lots of high calorie, low fiber/nutrient foods are not the way to go. As for cardio, I recently learned this: Find out what your target heart rate should be while exercising. Once you start your cardio regimen, get up to your target heart rate, and hold it there (+\- a couple of beats) for about 45 minutes. Also, if you belong to a gym (I belong to Planet Fitness, and love it), do a 30 minute circuit. All of this should be done 3 times a week. If you can't get to a gym, then I would start with what and how much you, and then include some type of cardio at 3 times a week for at least 30 minutes.

Your calories are going to be the most important thing you can do to reduce body fat and "tone" your body. You can run, ride a bike, do squats or any other suggestion but if you are still eating more than you burn you will not burn much fat. You really have no control over where the fat comes off either. Just because an exercise targets legs does not mean the fat will magically leave that area first. Most people lose weight in their face first and I dont know many people doing face exercises. : )

So in my opinion the most beneficial exercise you can do is a full body movement that you will stick with. Elliptical or rowing machine would be great. This will lead to more calories being burned and make sticking with a calories deficit easier.

Absolutely true that spot reducing is a myth. My bulk left my waist and upper arms first -- places I didn't really care about. But it will eventually get to your calves and big-ole thighs, and toning the muscles beneath the flab will definitely benefit you. I stand behind my original post 100%.

Squats (all variations, try goblet and pile and one-legged), lunges (in all directions: forward, back, side, curtsy). And walking hills (or running) do the trick. Combined with of course your diet. Somewhat.

I find that no matter what I do diet wise, my legs will firm up with appropriate exercise. (arms, back and core on the other hand....require diet)