You'd have to state what you're trying to take pictures of.
I found by lots of trial and error, shooting my son's soccer games, that 200mm lens on a APS-C body can reach across the narrow dimension of a high school football/soccer field, e.g. about 160 feet, but no way near enough to reach the long way (net to net, about 350 feet).
Even 300mm on an APS-C is just at its limit if you're standing next to one net or goal, trying to shoot players at the opposite end, about 325 feet away, next to the opposite net or goal.
If you're shooting birds or wildlife, you have to get a feeling for how far away your subjects are. I have a co-worker friend, who has a less expensive 300mm fixed focal length lens for her canon, who uses a 2.0 teleconverter and its still not enough reach for some far away shots. And at that effective focal length of around 600mm, camera shake is very significant with longer shutter speeds.