You can simply buy 6 bomb formulae from a herbalist to unlocks this trophy / achievement. There's one at the "Herbalist's Hut" fast travel point in the south-east of Novigrad. He offers 8 different bomb formulae. This will cost you around 2000 crowns. You can simply create a backup save before doing this and sell all your crafting materials / alchemy ingredients to the merchant, then buy the formulae with the money. Reload your save game to get the money back.