Beans are pretty nice. With EHSP, it's 45 favor per bean. And you can get a lot of iMG for making them as well! There's lots of other things though. I donate music blocks and gems a lot. It all depends on what I'm doing that day.
Meat. Sure it's not worth much individually, but it piles up fast with virtually no cost in either time or energy if you have a decent sized herd. Petting and nibbling pigs is also a great way to get img with little energy expenditure. Milk is good too for the same reasons.
Not only do you get iMG from donating them, but you get iMG from making them. For example, I make about 180 beans at a time (cause I donate to the three Giants which are currently affiliated with the skill I am learning... don't know what I'll do when I learn all the skills... which should happen in the next week or so... anyways...) and I get about 10k iMG from making the beans, then about 15k or more from donating. So all in all, a good haul.
When my bags get too full with Musicblocks, I donate those as a way to get rid of them. I prefer to keep Gems and sell them for currants than to donate them. And always always use EHSP.
As far as the beans themselves are concerned I used to swear by Spice Plant beans, but I recently realized Fruit Tree Beans are the easiest to make. Beans however require A LOT of energy and your tank is at 640. May I suggest investing in some energy? At 4700 for me, its not enough to: harvest the items I need, prepare them AND make the beans. It usually requires for me to use two full tanks for all of it.