How can you put more items in your secret base on Pokemon emerald?

You can't actually put more items in your secret base in Pokemon Emerald. The storage space is limited and there's no way to increase it.

Here's what you can do to manage your storage effectively:

* Prioritize: Only store items you need for your current goals.

* Utilize the PC: Store items you aren't using currently in your PC boxes.

* Trade: If you have items you don't need, trade them with other players for items you do need.

* Sell: Some items can be sold for Pokédollars at the Pokémart.

* Recycle: Use the Recycle Shop to convert unwanted items into useful resources like Rare Candies and PP Ups.

Remember, the secret base is primarily for customizing your space and using the decorations for battle advantages, rather than being a storage solution.