If you really want to sell it off, you can try trading in the stuffs via One Utama Recycling program. If you frequent go to 1U then I would suggest you do this since you would also need to download the app, register for an account and get the points. You can use the points to pay stores within 1U or pay the parking fee. Toys can't be traded for points though but they will recycle it for you.

Alternatively sell it off to 3rd party recycling center, like Dacing Trading Sdn Bhd or any rec

Old gundam, cards and toys I would suggest you sell it separately via any online platform, or just donate some to Jumble Station

keyboard, mouses and old hardware can put together as electronics if sell to recycling center, old books and dictionaries can put together as papers