how can i get more space on my ipod Touch

Delete stuff you don't need or save stuff onto your computer before delete.

Or buy a new iPod with bigger storage.

Nothing can be changed inside the Touch.

You can piggyback a flash drive, and have access to that., as long as it is connected.

You may be able to use a cloud service (need wifi, and cloud service).

You can reallocate - transfer some files to a flash drive, increasing usable space.