I’ve heard that if one plans to do anything about facial hair, that is one of the best places to start. The reason is because if electrolysis is needed there has to be enough length of hair to grab onto it with the tool. So if one waits until well into the transition process, they’d have a lot of facial hair showing when they’d rather not have it at all.
Second would be voice therapy since it take many months of work to effect lasting changes. Unfortunately, neither of these are usually covered on insurance plans, so we tend to delay them in favor of other things that are less out-of-pocket.