Interestingly, there is another thread on this same topic:-
https://www.diabetes.co.uk/forum/threads/foot-cream.161269/
Oops -just noticed two others have posted this link here - sorry
You need something to moisturise the skin; vasline will protect the skin a bit but will not moisturise it. Avoid anyhting with lanolin in it cos of rare chance of becoming sensitised to it (eg E45 cream).
Why not see what your GP can offer? Main thing is to use it regularly, at least once per day
Best wishes