- Easy mode is a good way to get top tier crystals at floor 500 for your first time but you'll need crystalline and mythical for those crystal and Mythstone higher tiers to drop easier but one shot enemies at floor 500 is pretty efficient at getting high tier crystals.
However on harder difficulty like mythic 3, it's actually easier to get maximum gold find, luck and item drops and at floor 350 mythic 3 is where you find the crystalline set but on any difficulty you find the fabled mythical hat. Still, you can do real good dmg to floor 500 enemies as they hardly have as much HP as believed to be. If you can one hit them or close to it, it's even more efficient in mythic 3 for gettwaluable legends like cerebral Vortex and stuff. How?
Arcanist+ Ascendant, momentum with 100% move speed (40% by gear which is 2 move speed affix with dexterity and you can get the rest by skills such as sprint, coat, etc), adventurer to go with momentun as one option, pathfinder to go with dodge , defiant if you want and maybe affix like frozen to make sure frozen enemies explode.
With that, also add 1x 50% glasscannon, 1x 50% barbarian if need be , maybe 1x push the limit , elemental crits , 2-3x 100% ED and 2-3x frostbiting to multiply frozen exploding dmg by 3-4x every explosions for easy billions of dmg. That way mythic 3 can become slightly easier. Obviously use Ignore resist because that's a great affix for a newbie if not 90%+ weaken.
Also of course mythics such as cosmic orb , a chest mythic to do 3x deadly strike instead of 2 or a mythic that increase all dmg by 50% from bleed or pierce build. Sanctuary for survivability and a appropriate resource system for your build. Energy mythic regenerates 30% of MP every second but you get to deal very close to 100% bonus Dmg or double . Fury mythic regenerates if you spam primary skill and increase special skill Dmg by 50% which is still a lot. Also a head mythic related to MP or no such as harmony, desperation for running out of MP withou system or for a resource system such as Discordance.
Make great use of talents so you can try: Amplify 20, Empower 20, Astral 20 with 20 intelligence/Magnify 20 and Sorcery 20 /Focus 20.
Natures: you can try putting 6x of the elements nature from the beryl crystal for 30% ED which is big boost or you can add crit dmg or attack speed. As long as it really benefits your build.
Crystal affix: use thing like 1x crit dmg, 1x crit chance, maybe a weaken crystal affix (if not , use ignore resist legend affix on gear but weaken goes very good with Ascendant and Arcanist), 1x crushing blow for high floor (mythic 3 only), possible deadly strike crystal affix and maybe another crit crystal affix or a regen affix or some other you want. Of course if it's a farm build at say mythic 3 (most efficient for luck), use 1x luck crystal affix per character (that's without Epiphany set found at floor 600 epic). You can use crystal 30% dodge for Pathfinder.
Another way to achieve 350% crit dmg without 2x crystal crit dmg is just 1x 225% crit dmg crystal affix and a Rage Set affix at (5).
Hero point: put 20 in intelligence generally, 20 in fortune , 20 or so in your most used skills and 20 in dexterity.
Mythstone: Obviously add 2x 2+ all set Mythstone or alternatively use a Nadroji ring and amulet for the 2+ all sets if you have no elixir stone.In farm build easy or mythic 3 mode , you can use 6 socket per character and put the fortune Mythstone for item drops. You can get capped item drops very well (in hirling mode, item drops is buffed by 100% so all the more worth it because 300% item drops is very powerful which can easily be done on very easy or mythic 3). If you have enough legend crystal called ruby, you can add item drops affix on each gear which saves many slots from Mythstone but far more expensive. Sfill, it spends about 3 instead of 6 per character.
What items should you look out for? You should look out for : Unreal Hood/ Fabled Staff for the mythical set and for the free mythic slots which is useful for newbie; gemmed crown/glinting sword/slicer/dagger for the crystalline set which makes rarer crystals easier; Immortal wand / boundless cap for Eternalized set which can be useful to find eternal legends for converting to ultra rare crystal or to try on but this is best with good enough luck% and item drops; aethereal drain items such as aether crown and aether wrap for the ED% on gear which you can get on very easy mode for progression and it goes good with the Defiant legend you found; on mythic 3, you should look out for any Cerebral Vortex legend, particularly the ring and masochist legends for Push the Limit, Barbarian and WD% on weapon.
If you have other class hirling (best warrior because their items favour the wizard class a lot such as masochist axe with 100% WD to really boost your dmg), ease use them to make farming a hell of a lot easier.That doesn't mean to say single player farming isn't possible but just that it's easier with hirling.
Lastly, about the Mutiny Gauntlet, this is a good item because of the 100% ED to the gear which is useful before you get access to 100 WD% on gauntlet and defiant gives a straight up 25% dmg and when you're in sanctuary mode, your dmg turns into near 50% boost. Pathfinder with 40%+ dodge is very good too . Also great as dmg reduction although DPS is far more important in campaign and avoiding enemies is better than taking the hits. It takes too many slots for more HP and survival for floor 500 mythic 3 anyways so it's not usually worth it.