Mario & Luigi: Superstar Saga - Spiked Item Mania

Spiked Item Mania:

When you earn the spike badge, you can jump on the enemies in the adventure field for free items, XP and other junk. If your level is high enough, you should be able to kill them instantly for fast cash.

If you equip the Gameboy Horror SP, you'll get even better items

Get Unlimited Hee Beans:

Once you make it to Little FungiTown, after you face the big rock boss you can enter the gaming arcade, which is in the eastern part of town. Go up to the top of the stairs in the arcade. Beat the high score of the game on the right, which I believe is 200. You will win an invincishroom. Mario will eat it and become sick with the bean fever. The curing plant is found in the Guffahaw ruins. After Mario is healed, you can go back to the arcade. Play the same game again and every time you get a nice score which is easy you will get up to 9 hee beans. Do this until you have 99 beans, go to the beanery, and make yourself some drinks

Defeat Queen Bean:
To deafet Queen Bean, all you do is jump on her hands. To jump on her hands, you have to just go to jump and don't jumpon her head Press the left or right button on the Control Pad, then press A. Keep doing that to both her hands until they shring. She'll also make a big blast with her hands, just jump over them. Just becareful because if she gets close to you, she'll you her fist and she'll try to smash you, just hammer her hands. Once her arms shrink, she'll start spitting lima beans. If you jump on one, it will become a Beanie The small green guys you battle. If you get touched by one, you lose health. Just jump over them. Keep on hitting her on the head before she gets powered up and make her hands big again. That's how to beat Queen Bean.

Defeat Hermie The Giant Crab:
To defeat Hermie, you must keep hitting him on the head. To dodge his claws, look at his claws carefully. If it wiggles a little before it attacks Mario or Luigi, then jump. If it doesn't, then don't jump. He'll also spit big bubbles. You can hammer them. Make sure you have full Bros. Points attacks. Do Chopper Bros. and Knockback Bros. attack because it's best. Whenever he goes inside his shell, use Mario's Firebrand. Then you win.

Cheaper photo:
To the right of Beanbean castle in Beanbean town there is a photographer who offers to retake your passport picture for 100 coins. Talk to him. He will ask if you want your picture taken. Say yes. Then he tells you that it is 100 coins and asks if it's okay. This time, say no. Then he will offer it for 50 coins instead of 100.