1. What is AP?
2. How do you get it?
3. What do you do with it?
4. How do you get the AP avatar items?
Ty :)

1. Advancement Points.

2. Gained from doing things like battling, breeding, completing missions, nurturing etc.

3. > buying generator save slots
> buying party preset save slots
> buying base styles in the wardrobe
> buying wardrobe design save slots
> intended for there to be an AP shop feature at some point in the future

4. > go to wardrobe, locate desired AP buyable base style (has AP icon in top left corner)
> click the gold bag icon in the top left corner to bring up popup
> select 'unlock with AP'
> hit the 'unlock' button

AP Stands for Advancement Points, and you can get it through battling, breeding(20 AP per bred pets based on what I just checked), and I've heard some say through nurturing, though I haven't personally paid close enough attention to the AP to nurture ratio.

AP can be used to buy a few different things, such as more party pet pre-save slots(This would be for saving different party setups/teams you like), generator design slots(So if your current amount of slots isn't enough to save all your designs, and you don't want to delete slots or publically post your designs, you can buy more), Avatar design save slots(Same as the generator, just with avatar designs), and avatar base styles. You also need at least 10,000 AP to be able to hire a stable hand for your stables, who, for a price of gold, will feed your pets daily for you for whatever period of time you chose from the selections available.

To buy avatar base styles, you'll have to go to the Wardrobe. There, in the Avatar Base Styles section, you'd press the little button that looks like . Then you'd sort to which section you want to buy a style from; Eyes, Mouth, Nose, Eyebrows, Ears, Hair, Beard, Features, Makeup, and Tattoo.
To purchase an item you'd want, you'd press the little satchel in the corner of the item's image that looks like .
After there'll be a little pop-up asking you if you want to buy with a certain amount of AP or Diamonds, click the Unlock with AP option. After that, the previously grayed-out Unlock button will have lit up green, and you'd then click it to purchase the item.

In the future, there is supposed to be a full AP Shop planned to give users more options as to what they can buy with their AP, but that's not yet released.

Edit:

Forgot to include missions as a way to earn AP, so just wanted to thank Scathereoite for including it in their post. ^^

Thank you! This is really helpful! ^-^ The menus in this game confuse me so lol

Tyvm, this was super helpful! ^-^