If you have to ask you're not cut out for it generally. Being apart of the party scene to network with suppliers and clients is very important. Drug growing and manufacturing however is far easier to get into.
Growing with little to no processing is ideal. High potency, price, and stealth is also important. Acid is the perfect drug to manufacture for this reasons, but is prohibitively difficult to squire materials, equipment, and the skills needed to produce it. Weed is great to grow, it's easy, grows quick, and there's endless demand. It's also not worth a lot, is difficult to stealth (smell and size). I personally think mushrooms are great. With a good strain a single tub of mushrooms will yield a half pound of mushrooms. An efficient setup in a moderately sized closet will yield 6 lbs every 8-12 weeks. Cocoa and poppy (to turn into morpheme and heroine) are also interesting, although I don't know enough about the process to comment on those.
Then you either find a single dude who will buy in bulk to mitigate risk, or sell on the danknets, depending on connections and what the local market for your drug of choice is.