Belly Button Crusting Post-Tummy Tuck

The navel gets roughed up quite a bit during a tummy tuck.  There can be oozing of serum from the wound edge as well as sloughing of the epidermis of the stalk.  Together, these can create some unwanted crusting.  Thorough but gentle washing several times a day will eliminate it and eventually when the healing is complete, the navel will behave as it did before surgery.

Based on the picture you provided, your belly button looks normal for this point in recovery. Be patient with the healing process. Crusting is expected, due to some seepage from the incision. Allow the incision to heal and dry. Use of opintments and topical creams may irritate and cause complications. The best thing would be to leave it alone and allow it to heal before putting anything on it. Consult with your plastic surgeon if anything changes which could imply infection.

This is extremely common after abdominoplasty because the blood supply to the belly button is different from the rest of the abdomen.
Generally, it sounds as if you are doing a good job.
However, too much Neosporin may make a fungal infection more likely.
Neosporin may assist in healing but, in and of itself, it is not a great antibiotic.
There are beter antibiotic creams but they do not have side effects and generally should not be used unless an infection is present. They can cause delayed healing.
Also antibitic creams generally fight off bacteria but not necessarily fungal infections. Other medications called antifungal or antimycotic or fungicidal agents are used for fungal infections. In severe infections an oral treatment may be useful bu this does not sound like your condition,
I hope this helps but in any event seek the advice of your treating surgeon.