The best time to max your Ariral rep is actually at the day 8 picnic. Any edible item, including organic garbage and spoiled food, gives +2 rep at this time. Cheapest way to max rep is to just leave 50 cookies. Or more if you want to steal something of theirs from the picnic. (I usually grab the toy warp arrows since this is the only time you can get them) so I leave like 70 cookies to be safe.. Only 70 points to buy. vs shrimp which still only give 2 rep at this time but cost 15 points each. It's a bit reversed at the treehouse. Shrimp will give +5 rep, while any other edible will only give +0.5.