Depends on what you want: Infiltrator is good for bypassing Substitute, while Frisk can make a difference in telling you how your opponent's Pokemon is used, for example whether an Azumarill will have a Sitrus Berry or Choice Band.
It gets a little easier after you beat the Chatelaine at the 50th battle. After that every battle won gets you 7 BP. I'll attach it to a Pumpkaboo (different from the shiny one for your brother, which will have an Everstone).
Looking for battles. I go online at random times, but it's usually easy to catch me around. Friend Code is 0490-6259-3111. Need to get back in the swing of things. I'm in Pacific Time Zone, so you won't see me later in the day.