I've found the Gourmaryliss (I've likely mispelt that) fairly nice for mana, especially when feeding them high saturation and hunger restoring foods (like steak). If you have Pam's Harvestcraft, Toast is a fairly nice thing to feed them. Be aware when automating this flower, that any food fed to it while it is still digesting a meal, will go completely to waste. The time it takes to digest a meal is 1 second per shank of hunger restored by the food. This does produce a ton of mana, At full pelt with Toast, it takes a Gaia mana spreader to keep up with the production. You can always use less wholesome meals or just space out the feeds if you don't have access to higher tier spreaders.
I also quite like hydregeas (again likely mispelt) early game. I actually took my basic starter mana garden from
this thread. The only alteration i really make is the addition of the endoflame for burst mana if I need it.