I want to role-play a Skooma dealer and I wanted to know if you can make your own Skooma.

Sadly, no. At least not in the vanilla game.

Vanilla?

Vanilla means without 'mods' (or modifications). If you are playing on PC, you can download and install (and even make!) mods that alter and/or extend the game. The poster is suggesting that there are indeed (probably) mods that allow you to make skooma.

I find it amusing that Skooma is little more than a "Restore Stamina" potion in Skyrim, and the two primary ingredients in Skooma - Moon Sugar and Nightshade - don't have that effect at all.

My PC is too crappy to run Skyrim.