As for leveling just focus on the campaing and blue quest , theres no special need rigth here you`re gona notice eventually that you always are 1 or 2 levels ahead of the campaing quest line.
Dungeons are a bit tricky tho. As a KFM you`re a tank which means that in a party you should always be the initiator plus i think the kfm its the only class whit aggro (threat level) increase abilities, ironically as a kfm your sole defense buff comes from the “Counter” ability which in Tier 1 Stage 2 will heal you a bit of the dmg recived while you counter + gives a 100 % defense buff (pretty cheap compared to the 400% destros and Dancers can get while spining) that turns you into a pretty squishy tank if you think about it but not all is as hard as it sounds, to balance that “illucionari” Squishines you can use any of these methods :
1) While Pve , Dungeons, you MUST make good use of your steps ( QQ , SS , EE ) Foot work, And Shadow Dance , Share the same ability three which means that 3 points on it will upgrade both abilitys and each will regerenate 2% of your hp every single time you land a good step, i mean when the iframe activates ( invulnerability frames during the animation of the skill) besides if you invest 3 points on those you will get and extra secod of invulnerability and makes 4 secods of invulnerability if you use them properly.
2) The counter Tier 3 Stage 2 works almost as your steps do because it will give you 1 sec of invulnerabiliti ( an Iframe) afthe the block, block that you can actually spam¡ and you should¡ because every single ability blocked whit it will grant you 1 sec to move, scape, stun , ETC really usefull while being surrounded by mobs
3) Make a good use of your regerattives abilities, you have TONS of them most that any other character, some examples; Cyclone kick Tier 1 stage 2 its an AoE kick That will heal 10 % of the dmg done to each enemy ( lets say you hit 3 enemies for 1000 dmg it will heal you for 300 hp each time and it will activate each time you land a crit whit your Swift strike ” the 2 key” that skill also can be spec into a life regerenative one whit aoe , the tiger strike (tier 3) that has the same efect and your Z skill it will heal you in 2 ways 10% of the dmg done to each enemy it hits and 10% of your maximun hp just by landing it.
4) As for damage dealing techniques theres some any cancel combos that you should practice because out of them you can get top tier damage logs which wiill help you to keep the bosses aggro.
1.) KFM has an incredible amount of counters so use them instead, the sooner you learn it the better. Especially since some of the regenerative skills are utterly horrible compared to other tree branches, like the Iron shoulder one.
2.) You have a lot of disables, obviously not enough at lvl 18 but as you progress you gain a huge amount of stuns, knockdowns/knockbacks/knockups which make regenerative abilities unnecessary. Learn to chain them at mobs with higher HP pools to prevent attacks.
3.) As Loire mentioned the sidesteps are a MUST, not only are you able to dodge stuff with them, if you skill into them you also gain invincibility frames which are incredibly useful – especially in dungeons for boss skills that cannot be countered.
I just got a KFM up to lvl 45 during the last 2 days, not much fun early on, but once you get some lvls you will see how useful you become, just keep in mind that KFM has by far the highest skill cap – therefor mastering this class will surely take its time. Don’t give up it is definitely worth it. I can’t give you an exact leveling guide, since i played with a friend while lvling, but i can give you some youtube links that helped me out if you are looking around for basic, skill branches explained and recommended skill orders to develop your build.