If you don't mind that the ciphertext is longer than the plaintext, GCM is perfectly fine.
If you want non-expanding encryption (ciphertext length is the same as plaintext length), then GCM is not appropriate, because it is very weak when IV's are reused, and there's no space for the authentication tag (GCM without authentication is just a form of counter mode).
While it is certainly possible to modify GCM into something secure (for a suitable definition of secure), the modifications would be significant and you could hardly call the resulting scheme GCM anymore.
If you just have an implementation of GCM, I would expect it to be difficult to use that as a building block for a secure scheme in any sensible way.
If you have access to the components used to build GCM (the block cipher, finite field multiplications, etc.), then they may be useful for building a secure scheme.