At what hemoglobin level will I need a transfusion?

No definite level. This is a complex question. We would need to know what is the patient's problem . If there is no immediate surgical issue, then transfusions are given if there are symptoms like chest pain. If there is blood loss during surgery, then indications are different. At our hospital, the medical staff has said there should be no transfusions unless the hemoglobin less than 8 gm/dl.
Variable. In general terms, almost never above 10. Transfusion may be needed if hemoglobin is: below 10 in patients with severe heart disease or renal failure. Below 8 prior to major surgery. Below 7 with symptoms of anemia such as chest pain, high pulse rate, breathlessness.