Are you using the right herbs? Take a look at the map of herb locations:
http://www.ldwforums.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/146258/page/1#Post146258

Recipes in the game are not different except for the pitcher vs berry recipes and, no, you don't need higher level Alchemy to get potion results. The higher level Alchemy reduces blow-ups.