For Potion Maker you need to go alone and select "Relationship Events". And start making them one by one.
As for Vampire Princess and Gyaru, Gyaru is not (yet) a follower, but you can find her after speaking with his apprentice almost at the entrance of "Wilderness Town". He will ask you to bring her from "Titan Step" as she is collecting materials inside a cave which is at the left side down once you go into Titan Step. Find her inside, talk to her and she will ask you to kill a Special Golem which is inside the same cave. After defeating the Golem,go back to "Wilderness Town" and give her the stone the Golem dropped. After that, you need to start bonding with her, by doing missions or bringing her gifts (Highly recommend the 2nd one), but also you needto enchance your stats to actually be able to not black out when drinking with her at the bar at night. After that, you are pretty much done.
Vampire princess can be found North from the "Abyssal Woods", up to the "Ancient Castle". To get inside you need to accept a Quest related to Vampires/Non-death.(Can't remember where you acceptit, so check on the main city or maybe the "Camp for adventurers"). And after following up that quest, you can then go to the castle where you will recruit the Vampire Princess.
PS: I have the 0.8 E version, so if changes were made or smtg on the F version, apologies if this is not correct.