If you are still around, the first port of call should be Lawrence Principe's book "The secrets of alchemy", for a general overview. There's no need to read any other book by anyone else, except the early ones by F. Sherwood Taylor and E. J. Holmyard for other background. Most populist modern books (i.e. last 30 years) are not very good.
Depending how nerdy you are, and what precise decade you wish to portray, there can be quite large differences in what alchemy is and what you do in it.
THe topic is so huge and difficult that I could write a book about it. (Wait, I already did a 15k e-book on medieval and Tudor alchemy, which I could probably sell to you)
For more specifics about late medieval/ Tudor alchemy, try my blog:https://distillatio.wordpress.com/
The internet has a horrendous mixture of fact, good research, and bad research. Going back to the primary sources is a minefield for a newbie, since the ones available in English are merely a small slice of what was actually written, and therefore you end up with a false picture of the field.
Several of the works in the Theatrum Chemicum Brittanicum are medieval or Tudor: http://www.alchemywebsite.com/texts_Ashmole_TCB.html
The tricky bit is distilling out of the medieval alchemical works and modern research into them, something that you can show to the public. The first thing to remember is that showing magic tricks with water, or colour changing water and talking about acid and alkali, or making gunpowder, is totally wrong in every way possible.
But if I tell you all that I do, that would be akin to giving you all my work for free.