Okay in junk city you can acquire the "Double TB" skill, if you teach this to all four of your human characters and equip it with all four of them whilst they are in your party the effect will be cumulative which basically means you get four times as much TB from every battle. This extra TB can then be used to buy new skills, Items, Golems or even to increase your SP and making your characters stronger.

Hope this helps

A lot of people like to use Golems in their party all the way through the game, however Golems cannot equip new weapons and cannot use EX moves or learn new skills. Therefore it is better in the long run to simply use just the Human characters all the way through (with the exception of certain battles like against the Lord of Earth). The advantage of this is that you can acquire immensely powerful weapons for all 4 characters and you can teach them all some great skills which make them stronger than any Golem that you acquire. You also have the capability to use EX moves with the human characters which are the strongest and most useful moves in the game.

Hope this helps