Good news for non-crown players who can't afford the crowns or seeds that drop mega snacks. The seeds drop in Avalon are Evil Magma Peas and Deadly Helephant Ears, (of course there are few seeds from crowns drop as well). Some people said that all of bosses drop those seeds, so keep your eyes on those seeds and bosses names when and whoever drop the seeds.
Do you remember my "$$$ on Mega Snacks Pack"? Its explained about compare mega snack pack and seeds.
If you really wanted those seeds that drop mega snacks, save your crowns, go farming at Avalon, the bosses are drop those seeds. But I suggest to finish Avalon, then focus on farming later. Which will be easier for your plans.
I wish you Good Luck with Spiral!