Should "Clienții mei nu mă cred pe mine" be accepted?
Yes, this would be correct, but „mă” already implies that the clients do not believe me (rather than someone else). „Clienții mei nu mă cred pe mine” would be an overstatement and sounds a bit awkward, but is per se not wrong.
Can it be "clientele mele" if the clients are female?
Sure!