Hi,
It definitely isn't limited to diabetics.
My husband had a varicose vein op nearly 30 years after he developed a problem - which had developed in his teens.
And many women develop them during/after pregnancy.
There are a lot of things you can do - support stockings, exercise, weight loss, keeping feet elevated, etc.
But if the problem is due to a varicose vein, then the ultimate solution is an operation to remove the problem.
There are additional problems that diabetics can experience (but again, not exclusively restricted to Ds) due to circulation and nerve damage from raised blood glucose, over time.
Have a google, and you will find a lot of information under varicose veins, peripheral arterial disease (PAD) and poor circulation.
You may find these links useful too
http://www.livestrong.com/article/309105-why-do-diabetics-have-bad-circulation/
http://www.healthline.com/health/poor-circulation-symptoms-causes
I had a quick look for links about improving circulation, but nearly all the links I found were selling some amazing gadget to do the job while sitting in an armchair. While some people have to sit all day for other health issues, the rest of us benefit hugely from moving about and walking - which helps the blood pump back out of the feet.