Is a generic contact lens cleaner okay to use?

Okay, so I got my first pair of contact lenses last month, and my optometrist gave a Opti-Free starter kit, which included everything, even a cute carrying bag. He then tells me that he only recommends using either Opti-Free or Bausch and Lomb contant lens solution because store and generic brands are not trustworthy. Well, i am now out of solution, went to go buy another bottle and realized how expensive they are! The Equate (walmart band) is a third of what Opti Free costs and I am on a tight budget! Is it okay to use this once?