Dragon Age Inquisition

You can start upgrading potions in Haven with Adan, and once you progress the story, in Skyhold, in the crypt next to your throne.

Upgrading potions requires a lot of ingredients, so it's advisable to collect all plants you see. Also, each region has it's own set of reagents (though some common plants like elf root of blood lotus seem to grow almost everywhere). Hence, whenever you have enough power available, open a region, and do a sting hunt for some reagents. Once in Skyhold, you can also get access to 'retrieve resources' missions at the war table. Send either Leliana or Josephine to bring some reagents (usually around 6), but never Cullen, as he seems to focus on metals. Also in Skyhold, once you have access to your garden, every time you harvest a plant in the wild, there's a chance you get seeds to plant in the garden. Finally, you can also purchase over-priced reagents from some vendors, which I don't recommend.

You can find the ultra-rare plant Prophet's Laurel on the Storm Coast, in a cave in the most south-east corner of the map. That cave also holds a rift. Every time you enter the map two plants spawn in that cave.

The following list is not complete, but there are more than enough to get you the achievement. I'll update the list if I find any of the remaining recipes. I'm not typing out all reagent requirements as you can easily look them up in the game by approaching the potion upgrade bench.

Healing Potion 2 upgrades

Regeneration Potion 6 upgrades
*Missable* Speak with Adan in Haven to receive this recipe for free.

Lyrium Potion 4 upgrades
*Missable* Retrieve Taigen's notes for Adan from the hut north of Haven.

Rock Armor Tonic 5 upgrades
Hidden in the tower ruins just west of the 'Thelm Gold-Handed, the Dreamer' landmark in the Hinterlands. Use the search function to reveal it.

Healing Mist Grenade 3 upgrades
In Crestwood. After taking Caer Bronach, enter the caves underneath it. Defeat Snowball and loot the recipe from her corpse.

Antivan Fire Grenade 5 upgrades
Buy the recipe from the merchant at the Crossroads in the Hinterlands.

Jar of Bees Grenade 5 upgrades
After recruiting Sera, do the 'Red Jenny: Inquisition Needs Beeees!' quest on the War Table.

Pitch Grenade 5 upgrades
In Valammar, behind a breakable wall (requires a warrior).

*Added:

Tears of the Dead 5 upgrades
Acquired in The Fallow Mire for completing the 'Beneath the Mire' quest. Best done in tandem with 'Beacons in the Dark'.

Confusion Grenade 5 upgrades
*Missable* During the mission 'Wicked Eyes and Wicked Hearts'. After you climbed to the balcony, solve the bust puzzle in the Grand Library and loot exposed crypt.

This was one of the last achievements I needed for the game and I thought it was going to be such a grind getting the herbs for the upgrades of the little potions I discovered. 40-60 herbs per upgrade for some of the bombs? That's ridiculous.

I traveled to Val Royeaux and walked over to the merchant on the bottom right. He sells you Elemental Resistance potions (Fire, Ice, Lightning, Spirit) and the upgrades for those potions only require 5-10 herbs (I think it was mostly rashvine). Either way, you can get more than half of the required upgrades from these.

The other half, I just recommend picking up all of the herbs that you come across while playing the game normally. If you have some spare inquisition perk points then you can get the large assortment of herbs (I was given like 80 of them) which helped immensely.

If you don't want to farm and you have the tresspasser dlc you can wait until you get to the dlc then just buy all the herbs you need to upgrade potions. Bring a decent amount of gold for that though