The best thing for foot drop I have found is exercise. Don't just concentrate on the ankle, however; exercising the hip will actually help your foot pick up better.
Exercises I perform regularly are:
Clams (lying on your side with knees bent, and lifting the top leg, keeping the feet together) Side leg raises (lying on your side, keep the bottom leg bent, and straighten the top leg and lift)
I also perform several leg strengthening exercises using resistance bands. If you do a Google search, you will find lots of exercise suggestions online. Trevor Wicken runs an online 'MS Gym'. He can be found on YouTube and also Facebook.