Edit: Since I'm at the top of the page, I'll mention another mask that is highly useful, perhaps the second most useful after the Bunny Hood - the Stone Mask.
How to get it and what it does:
I always had a routine -
That's an immediate 200 rupees that can be stored in the bank.
And yes, if you want an extra 200 rupees
How to get it and what it does:
To get this mask, once you have the Lens of Truth try using it in the entrance to Ikana Canyon and see if you can spot anything unusual in the area. It helps to bring along a bottle of red or blue potion with you! The effect of this mask is that while you're wearing it, most enemies will ignore you. It's useful for avoiding unnecessary, time-consuming confrontations.
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Get the silver rupee in East Clock Town every time you play the song of time. Then deposit it in the bank. Eventually, you'll have a ton of rupees, which can come in handy later.
I always had a routine -
get the Silver Rupee on the roof in East Clock Town, then go to the path that leads to the Astral Observatory and break open the hidden wall to get the second Silver Rupee. Having the Bomb Mask helps, since you lose all your bombs whenever you warp to the beginning of the first day.
And yes, if you want an extra 200 rupees
the big bird that hovers around the entrance to the ranch in Termina Field can be slain for a big reward.