You really can't go wrong with getting Dendrobium, whatever else you decide on; she's a beast now and just gets even more beastly in the future. Acacia, Kerria or Alpinia are all solid choices for the slash spot. Iberis is quite good, and Sakura is a nice sideboard choice for raid events. All of these units are also future-proofed in the sense that they have bloom forms as well. Oh, yes, Saffron is a goddess of defense in the future; right now she's not terribly special but worth investing in.