Cherrim is alright ingame. His ability makes him useful. Here is a good moveset.
Cherrim@Heat Rock
-sunny day
-solar beam
-aromatherapy
-hidden power ground/fire
Sunny day activates Cherrim's ability flower gift, making it usable. With sunny day, solar beam owns. Aromatherapy heals, and hp ground/fire is for coverage. Heat rock makes sunny day last for eight turns, increasing it's use. Hope this helps!