Do you mean using Disney transportation or your own car?
Using Disney transportation, we always allow an hour before we want to arrive (so we show up at the bus stop one hour before). That is a safe cushion even when you might have to wait for the bus.
By car, I'm guessing you will be from the AKL parking lot to the TTC in under 20 minutes. But then you will have to take the ferry or monorail to the Magic Kingdom entrance (and the tram at the TTC parking lot, unless you park near the front of the lot).