I am assuming you are meaning a heelside back roll or a toeside front roll for a "front flip" and a tantrum for a "back flip"
speaking in wakeboarding terms a front flip is a much harder trick to do, because the board is going end over end vs side to side. a front flip definitely should be saved for later.
I would try either a tantrum or a heelside backroll first. i personally did a heelside backroll first. though i listed the backroll as what you call a "front flip" it is not so much a front flip really. the quickest and most accurate way to describe a back roll (IN MY OPINION) is that you keep edging up the wake on a heelised jump... as if the wake was a giant tube or loop. it is not a trick you have to huck or generate a ton of speed for.
AGAIN, you will be going for either a TANTRUM or a BACK ROLL.
P.S. the tantrum is a laid out "back flip" on a heelside jump.