First I think you should pick a target drug that you want to synthesize and then try to gather as many information about it as possible.
Read into literature that provides knowledge about this drug.
Most likely there will be several synthesis routes available for this drug, pick one that is the most suitable for you (a route where you will be able to source all ingredients) and then try to learn about every step involved to finish this route and synthesize the final product successfully.
Here are some topics that might help you:
Book about the set-up and operation of clandistine drug labs:
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ttp://b bzzzsvqcrqtki6umym6itiixfhn...eration-of-clandestine-drug-laboratories.119/
Steam Distillation:
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ttp://b bzzzsvqcrqtki6umym6itiixfhn...xf2qgyd.onion/threads/steam-distillation.578/
Extraction:
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ttp://b bzzzsvqcrqtki6umym6itiixfhni37ybtt7mkbjyxn2pgllzxf2qgyd.onion/threads/extraction.553/
Vacuum Distillation:
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ttp://b bzzzsvqcrqtki6umym6itiixfhn...nd-application-of-vacuum-in-a-laboratory.813/
Home Filtration Set-Up:
http://bbzzzsvqcrqtki6umym6itiixfhn...ry-diy-exhausting-fan-models-and-filters.471/
Use of Rotavaps:
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ttp://b bzzzsvqcrqtki6umym6itiixfhn...gyd.onion/threads/used-rotary-evaporator.478/
While the above shown information can be very suitable for the routes I choose for my products, your products could require completely other routes.
Start with defining your product first.