Well, if you are using it as a generic noun referring to the "Banking sector" or the "Business of banking" the proper spanish word would be Banca.
If you use "Banking" as an adjective, as in sentences like "Banking account", "Banking fees", "Banking terms" and such, then the transalation should be bancario or bancaria depending on the gender of the noun they go with.
However if you use the word "Banking" as a verb referring to the act of "engaging in the business of banking, maintaining savings and checking accounts and issuing loans and credit, etc" then there is no exact match in spanish language, as it happens with many other english words.
The thing is in english you can use any noun as a verb, but you cannot do that in spanish, so usually it is necessary to use a longer expression in the translation.
I wouldnt be suprised if in some south american country they transform the english verb into an anglicism such as "banquear" (Im pretty sure spanish population in USA does that) but in proper spanish you would have to say something like realizar operaciones bancarias.
I hope this was helpful.