Weeell, I can get that much from a large quoin (or buy 4 or 5 from one qurazy quoin) so I really find them kind of cheap... Not that I'd want them to cost more! Any cards under 3,000 iMG I buy right away because I gain that much in only a few minutes of playing.
Edit: Especially since they are cards you can trade and sell to other players, they certainly need to cost *something* :)
Auren means the re-shuffle cards that appear as upgrades. As for what I do: I Reflect all my icons, garden, make items and donate them to shrines (both of which give lots of iMG depending on what you make) and run around the Ancestral Lands (which in itself, on a good day, has given me over 10,000 iMG before I get booted out :D). I also like to pet/nibble pigs and sing to butterflies if I happen to have lots of energy.
You get one shuffle per game day for free. That's 6 free shuffles for real, 4 of which are easy to schedule.*
You can buy shuffle cards and sell them to other players for far more than they cost you. If the cost is too high, I suggest that you buy them and use the currants you get from selling them to buy things to donate to earn back the imagination you spent.
*no, I don't mean get up in the middle of the night. Shuffle at 12:50 pm (noon) and 1:00 pm. Then shuffle again at 8:50 pm and 9:00 pm. If you're really intense, you can get in the remaining 2 shuffles early in the morning at 4:50 and 5:00 pm. These times are all Eastern Daylight Time, but the scheme will work no matter what time zone you are in. An easy 4 shuffles, 8 hours apart.
Ah, yes, the extra redeal cards...I look at it as I already get one free redeal a game day. IMO, it's cheap to buy an extra one for when I really, really need to change my hand. And if I don't want to spend iMG on an extra card, there is no reason why I have to purchase it.