Good luck getting gammabutyrolactone in the US. If you manage to get it you mix it with a strong base (lye or KOH works best) in equimolar quantities. I hardly consider it synthesis. Becareful because bases burn horribly, you don't want GBL in your eyes, make sure to dilute the GBL and base with water first.
If you find it be warned that it is extremely addictive and possibly the worst kick known to man.
The Colorado River Toad does not produce DMT, but rather 5-MeO-DMT. Do some research about it. I have no idea how one gets it out as I refuse to harm a living thing in the name of getting high.