i would either get a puffer, and nothing else.
or no puffer, and a couple lil brackish fish.
no fish is really safe with a puffer, in my experience. (nippy lil fish)
but at the same time, they're all cute and bubbly, and rush the tank to say "Hello!"
here's an idea, dont know how set on brackish you are, but i think a real tight set up for a 29 gal would be a heavily planted FW with cherry shrimp, ghost shrimp and like 4 or 5 Dwarf puffers. (1 male, the rest female, and that might be too many, ask puffpunk)
you'd spent most of your money on plants. you just gotta break the puffers lines of sight. i think thatd be really cool.