You can also strengthen your ankles by doing some functional training..... Perhaps try doing some exercises while standing on one foot....even brushing your teeth, doing the dishes,... (don't smirk til' you try it).
Try shoulder presses or raises,
bicep curls,...standing on one leg, then on the other. Try 1-legged DL's or stork stance with a barbell or DB.
Jumping right into wobbleboard training may just cause you to sprain your other ankle if you're not careful....have you used 'em before? They're a challenge, they're fun, there are also other things out there to accomplish ankle strengthening and balanace.