I would be adding some shelves in, so your hamster hasn;t got a big drop to fall if he/she climbs up the bars.
Things like cork tunnels/branches/wicker tunnels etc are good too. You can also use boxes from your recycling.
Like Nibbles said a hideout for sleeping in too is a good idea.
I have a couple of videos that might help:
Setting Up The Savic Plaza Hamster Cage 2020 | Cosmic Hamsters - YouTube
Cosmic Hamsters: Budget Hamster Cage Setup, Using Recycled Items - YouTube