Feathering Prop
I'm not an Oceanis owner but a sailboat owner and the single item I'd choose to upgrade performance is a feathering or folding prop. My boat has a Max-Prop sold through PYI at www.pyiinc.com. They're not cheap, about the price of a good 150 jib but it will increase performance on all points of sail.As for a cheap item, I'd add a backstay adjuster, block and tackle vice expensive hydraulic.The third item I'd add is a cruising chute, something like the North Whomper or equal, for sailing off the wind or on a broad reach. It would depend if you sail in a channel where tacking room is available or not. If you typically sail to weather or dead downwind the high-clew type sail probably won't be that much help. In this case I'd suggest touching base with a few local sailmakers (in fact, I'd probably do this anyway) to find out what they'd recommend.There you have it - my two cents worth. What do you think?