If you fishless cycle a tank then it's capable of processing 5ppm of ammonia, far more than your fish will produce, so you can fully stock at once if you like.
If you are adding them in stages:
1. If possible only add juveniles, they're less aggressive when they are younger.
2. Add in order from least to most aggressive.
3. Rearrange all your rock work/decor before adding any new fish to break up established territories.
4. Right before adding your new fish, feed the existing ones on the opposite end of the tank.
5. Turn the lights off and keep them off for at least 4 hours after adding new fish.
6. Add new fish in groups, don't just add one or two as they are more likely to be harassed.
If you use those techniques you'll have a pretty good chance at avoiding major aggression. However, with mbuna there's always a chance the newcomers won't be accepted, so observation is important.
