Outside of Alfred and the Bat-family, Batman doesn’t have many allies in Gotham. One key ally is Jim Gordon, who is sometimes the questgiver with the Bat-signal, sometimes the one honest cop who has to hunt Batman down, and sometimes a detective story character in his own right, complete with a family member or two of his own, one of whom might be important in some continuities.
For a crimefighter, a friend on the police force can be vital to get clues and avoid being shot by SWAT teams.
Someone with medical training to patch up your injuries with no questions asked is pretty useful too. Dr. Leslie Thompkins is less prominent than Gordon (she wasn’t around in 1966, so she missed out on day-glo TV stardom) but she also acts as a moral compass and sounding board for whether he’s gone off the deep end.
Tech support is provided by Lucius Fox, among other people. Those wonderful toys don’t come from Forbidden Planet in-universe, after all...
Crimefighters often have petty criminal contacts to shake down for information. Batman uses disguises to fill this role himself.
A plucky reporter could be handy as well. Batman never really got one of these as Superman and Lois Lane had that covered already, but Vicki Vale pops up now and then...
What else do your PCs need regularly? Who do they talk to about their adventures, seek advice from, sometimes bring along? Which contacts are strictly business, and which are friends?
How do they react when someone who helps them needs help in turn? (Don’t do this too often, especially with “bought and paid for” NPCs like Allies and Contacts in The World Of Darkness - something a player has spent resources on shouldn’t be more trouble than it’s worth.)