for Feliar you can use a love potion on him.
other than I only have something if your good using the cheat menu to make it less grindy. just grabbing every gift you need from the menu instead of actually having to grind them from the places they originally are from, and one in specific is really good for maxing like on Feliar, which is his rare coffee Vicoria stole. you can completely max him if you just grab like 20 of those from the cheat menu. you can get more than one in base game but cheating them doesn't limit the boost you get from it.
no idea about other things for Vicoria though.