With GABA there seems to be a lot of dispute on if taking it orally even works, as a lot of people/research says it can't cross the BBB (at least not noticiably without a mega-dose). On the other hand, there are some people out there who I've read have had success with it; who know's if it's placebo though.
If you want to try to increase GABA directly you'd have more luck with something like Phenibut, which in effect can cross the BBB and agonizes GABA once across. The problem is it will have withdrawal effects if used everyday/long term. It's compared a lot to benzo's, especially valium (a lot of people say it's like "time release valium"), and works under at least some of the same mechanisms.