To get started with juju potions you'll need vine herb seeds for the herbs and the secondaries for making the complete potions. You can obtain those by talking to the Witchdoctor at ;;home and buying some Marasamaw plant traps.
Then ask him to teleport you to the jadinkos. They can be caught using the plant traps (in a similar way to box traps) and yield various seeds and/or secondaries. God jadinkos are special they can drop harmony moss seeds, and are only available for a set amount of time each day. They're always available on weekends.
You can plant your vine herb seeds in vine bush patches, and you can get to the patches by talking to the Witchdoctor. All seed types take 80 minutes to grow and will never become diseased and/or die.
Once you have herbs and secondaries, you can begin making juju potions! Here is a cheatsheet for them. You can also examine juju potions in-game and they will tell you their effects.
If you add harmony moss to certain 3 dose juju potions, you can make 'perfect' juju potions which have better effects and last much longer. Here is a cheatsheet for perfect jujus. You can examine these in-game as well.
In order to grow harmony moss, you must have access to Priffddinas. Talk to the Witchdoctor and ask him to take you to the harmony pillars, then rake the pillars to reveal what skill the pillar is attuned to.
Then you can either plant a harmony moss seed, or wait until the weeds re-grow in order to re-attune the pillar. Once a harmony moss seed is planted, gaining 75,000 XP in the attuned skill (NOT affected by XP multipliers or bonus XP) will grow the seed a stage. After 4 stages the harmony moss will be grown and can be harvested.
Juju potions will be released in Patch #43. Hope you guys like it!