It depends on where you're at progression-wise, honestly. I've been using Floating Hydroangeas in combination with 3x3 water cells to act as batteries which has proven more than adequate for tier 1. Tier 2, sustaining the elven portal, is something else entirely. I'd advise checking out the botania subreddit to see how other people are handling that, as I am dumb at best where automation technology is concerned. You might also check the Community Showcase section here on the FTB forums, where I know there have been a few example setups with pictures that show a couple ways to automate several different kinds of flowers.