What is the adverb for skimpy?

There isn't a single perfect adverb for "skimpy" because it's a descriptive adjective. However, depending on the context, you could use:

To describe the amount or quantity:

* Scantingly: "The meal was scantingly served."

* Sparingly: "The information was given sparingly."

* Meagrely: "They were meagrely compensated for their work."

* Minimally: "The design was minimally decorated."

To describe how something is done:

* Scantingly: "They were scantingly dressed."

* Barely: "The curtains were barely covering the windows."

* Tightly: "The clothes fit tightly."

To describe a feeling:

* Slightedly: "She felt slighted by the skimpy portion."

* Scantingly: "The explanation was scantingly provided."

The best choice will depend on the specific situation and the desired emphasis.