To clear the small confusion,
GSync/FreeSync is arelatively new technology which is far better than VSync and adaptive VSync.
Adaptive VSync is only VSync but slightly modified
GSync is more or less an overpriced FreeSync.
About the more cheaper solution to GSync (aside from VSync or adaptive VSync):
Unfortunately, if you have nVidia GPU, there is no cheaper solution than GSync.
Freesync monitors work only with AMD cards and not compatible with nVidia cards (also vice versa for GSync).