For medicinal use of your gabapentin, take it as prescribed. If the prescribed dosage is less than effective for pain relief (NOT getting high ;-) ) then bring it up with your practitioner. It's unlikely that you will be prescribed a dose that hits the effective ceiling of gabapentin (around 1800mg at a time).
For recreational use, take with a high-fat snack or meal. Some say that combining it with naproxen produces a synergistic effect, but I don't know if that's true. Too many NSAIDS are bad for you in a lot of ways. I /think/ gabapentin is a drug effected by enzymes much like opiates, so ranitidine or white grapefruit juice might increase effects.
Note: these tips can also be used to maximize medicinal dosages. I highly suggest, hope, and recommend that you not drive, operate heavy machinery, or the like if you are not sure of the effects you're producing. Don't endanger yourself or anyone else, please.
That said, some people report sedation with gabapentin, and I'd imagine that lorazepam would increase that. I'm not sure if it would cause respiratory distress or other life-threatening effects, so do be careful.
I don't think that such a low dose of gabapentin will interact too badly if taken alongside your Ativan. You don't need to worry about staggering your doses; you're nowhere near the mg that will result in steadily poorer bioavailability.