1 black magic is powerful but dark, closer to a demons power then anything else and will most likely kill you if u try to use it without training and can rip your soul apart if u try to kill anyone else
2 white magic is healing magic, generally used by good people for tiny spells like making rainbows, summoning unicorns, healing people, animals, and plants (not designed for killing)
3 gray magic is more powerful then white magic as its a mixture of black and therefore its harder to control (black and white don't like each other) most of the time people try to get this power and end up dead it takes a lot of self control.
if your born with gray magic then you should have a easier time controlling it if you where born with black magic then you should really consider learning white to control it otherwise you could turn into a demon and you know, eat someones soul by accident, that would be bad. if you where born with white magic then your fine, don't learn black magic, learn how to make your magic stronger. white cant become gray or black unless by force (mind control, potions etc)
so to answer your question. it depends on what magic u have what magic you use. white or gray is the best. dark magic can control demons if you know the correct spells.
extremely powerful white magic users have been known to have the power to summon angels particularly the archangel Gabriel or Michael
if you find u cant use magic (not born with it, cant direct it etc) you can use salt, holy water, or sage
or if your extra careful make a kind of paste with mashed up sage in salted holy water (should look like a green paste) use a mortar and pestle
DON'T TRY TO GET POWER IF YOU DON'T HAVE IT
if you try you may get killed, deformed, or worse (like accidentally summoning a demon and then they eat your soul)
i use gray magic