My girls share a room and I have a no toys downstairs rule! You need good storage - ikea kallax is brilliant.
Things I bought and don't take up too much space.
Busy books - normally £5 has a book, 12 figures and a playmat. Different films/characters, I buy with the corresponding dvd and story book - this year zootropolis and finding dory :)
Fold up tent - ikea £17 brilliant value and size folds down and is tucked behind the bunk beds when not in use :) Wow gift too set up in front room!
Arts and crafts - they get used up so no storage issues!
Figures of current favourite characters - this year pokemon, teen titans and paw patrol.
Personalised story books - lost my name and magic chair are both lovely books :)
Playmobil carry cases - all fits inside.
Happyland - quite big but perfect for all the character figures and normally much better quality.
Fleece blankets, new cup/plate/bowl, bedding set, towel, clothes in favorite character.
Top trumps - more for older but fun game.
Kiddizoom camera - big hit being able to take own photos and play the games (still used at nearly 8)
Books!!! Favorites here are sue hendra (all hers are brilliant!), the dinosaur who pooped series, Julia Donaldson, mog, the fairytale hairdresser series and kipper.