For seed oil, melons are the best. They grow super fast, and convert to multiple seeds.
I am running my whole base (MJ side anyways) off of seed oil only. I got melons in a trade with a villager.
I just redid my melon farm and upgraded to a smart straw golem and a perceptive wood golem to tend to it. A regular straw golem will work fine if you just have a melon or pumpkin farm. For the size farm I had, a regular wood golem couldn't get to the corners. Now every available space except for the water blocks and chest block grow some type of crop. The excess wheat and sugar cane will be converted into IC2 biofuel to burn in a diesel generator from GT. I planted potatoes, carrots, wheat, sugarcane and flax in the previous dead space between the melon rows.
I have 2 squeezers running 4 biogas engines running on seed oil currently. I still end up producing more seed oil than I consume.
*Edit* There is a transposer under the chest pulling everything out and sending it to be processed.