Barley is the best and wheat is second best. I get organic seeds/feed for something like 37 cents a pound. Each grain varies. I tried oats but am not as pleased. This is what I do.
Buy some cheap plastic dish pans, or if you are unlucky you might have a supply of the plastic tubs from hospital stays. Drill very tiny holes all over the bottom of the pans. You will need about 10 pans as it takes 7-10 days for the sprouts to grow to optimum size. Soak the seeds in a bowl for a few hours or overnight. Next, pour the seeds into one of the plastic pans. Rinse well with water that is neither cold or hot. Allow it to drain well. Now you will need a much larger shallow plastic tub to set the sprout tubs into. Cover tub with a damp dish towel. Seeds/sprouts must be rinsed at least 3 times a day to keep them fresh, hydrated, and mold free. Seeds should be maximum of 1/2 inch deep when initially put in drainage tub. You will know they are ready when they look like new spring grass about 3" tall. I sometimes let them set out near a window on the last day of growth to allow them to turn as green as possible. They will also have a nice mat of thick white roots. Yum Yum. Ready to eat. Ducks and chickens love it. Would also make great rabbit food. Start a new batch every day. I cannot believe how much money this has saved me with my feed expenses.