I got a DDT nib, which made it easier to get 190 aspd without AGI/berz pot (especially on my knight), but DTT is obviously better for a LK since with frenzy you can get 190 aspd if you have a berz pot.
Anyways, good gears if you like a crit build with frenzy (bear in mind that there's no way to swap gears in frenzy):
-DDT/DTT nib (preferably DTT, and you really can't do without it)
-Dual deathloop kobolds (or brys+brys/brys+meg)
-Gryphon headgear
-Valk helm (kaho if you don't have one)
-Deviling (obviously)
-Fire armor (Tao Gunka fire armor is the best, but it's a little pricey and pretty useless for any other class)
-DL sleips (the extra hp/sp bonus as opposed to valks is better, only downside is it's hard to escape from mobs)
-Penomena Shield (reduces damage from formless by 50%, but balam's idea of using Maya might be better)
Practice a bit, it's not hard to learn. The technique (like balam said) is to buff, frenzy, kill, then when your hp is low go somewhere in a corner where there are no monsters and relog, then use GJ and re-buff and re-frenzy. Carry flywings in case something comes out of nowhere when you relog, but otherwise there's no need for healing items whatsoever. Be sure to use all the LK buffs, as you will notice a definite damage increase, but the water Warm Wind is most important as that doubles your damage.