Okay I don't know if this is the right place to put this. I am sorry if its not.
so I am new and there are things I still don't understand yet.
how do you get map pieces?
what are stickers and what are they for? honestly, I don't know what to do with a lot of stuff I get. the minions and plushies and I have like a beanbag chair and cleaning spray in my inventory and have no idea what the point of them are. I feel like there is probably a large chunk of the game is am still trying to figure out.
Here's some info for what you asked.
Map pieces are from random events or buy the pieces from user shops.
Stickers are a collection item. You can have them stuck by the hustler on Atebus for a fee, or other users can stick you, and you can stick them to other users. There is often people willing to help to put your stickers on you.
Beanbags and plushies are also collection items. You can pop them into the collection yourself. It will either give the option or tell you its already in the collection.
Collection items usually earn you trophies after you collect a number of them.
I'm sure you have a lot of questions, and let's start with the ones that you mentioned.
Map pieces - You get them mostly through random events, but you can also purchase them from other users' shops.
Stickers - If you go to the "Games" section of the site, there's a section for "Collection". There is a sticker album, and you can ask others users to stick stickers to your album or do it yourself at the Hustler at Pina Park.
Plushies and Beanbags can also go in Collections. Once you put something in a Collection, you cannot take it out with the exception of the Minion Zoo.
There are a lot of items that do nothing, but can be asked for as part of quests or used as interesting items for a pet's treasure chest.
Also, if you haven't looked at it, you may want to look at the Subeta FAQ for help with some other common questions.
Subeta's just for the lulz, none of the virtual items here are "real" as such they're not "worth anything" except we are licensed to use them to play around with.
The site does have games. Many of the collection items you have listed have Achievements which are like little gold star stickers you might get for good behavior in school. It is possible to battle with your pet if you like to play wargames. It is possible to play a trading/selling game with all of the virtual items, treating them like a real-life stock market.
The site has a creative side. It is possible to play dress-up paper dolls with your Human Avatar, and there's quite a bit of flexibility and creativity in this as you are allowed to create your own wears, many of which would not work at all in real-life or which would be a pain or too expensive. It is possible to use coding to modify your pet's image and their pet pages. Or you could just chat with your friends here.