"First off, defense and protection are the keys for success. I only have 1 nuker, so here is my build. I am a Fire, Light, Cold, and Heuksal nuker. My masteries are, as of right now, 77 Fire(maxed to 71 to de-lvl and farm later @ lvl 80), 70 Light (maxed with buffs, passive, Grasswalk and Phantom, and nukes), cold to 63 for buffs, passive and snow shield only. And Heuksal is lvl 60 with Soul Spear series maxed and passive only.
Now, how to lvl a nuker (for me anyway), is to grind on mobs higher than yourself that you can safely 2 nuke to kill them quickly. If it gets too tough at 6-7 lvls higher, lower it to 1 nuke and your highest lion shout per kill. Use the fire as imbue and the fire nukes hit the absolute hardest. I have light nukes that i use now, @ 77, to get the mobs to gather around me and kill even faster. I have 8k HP at lvl 77 .
I farmed the common way at or near the stronghold with a bow and de-lvl'd it all away to make way for the current trees. I zero gapped once I was done farming about 150k to lvl 52 where i found a SOS spear and got it +7 to farm another 55k there. And I zero gapped till now when i will be de-lvling when i hit the cap to farm the rest of my build. I plan to have 80 Fire, 80 Light, 70 Heuksal and 70 Cold for buffs and snow shield.
Once again, gear is the most important thing you can spend gold on. A weapon is nothing if you die every two mins. I spent all my gold on good Armor up to and including the 8th degree. I had SOS +3 complete set of armor. Now i have all 3rd tier protector thats +4-5 every piece has decent %'s and good blues. My Spear is 72+5 good %'s and full blue. With that, i was killing Niya Royal Gaurd at lvl 72 and Niya Mages at 70.
So, in short, buy the BEST gear you can afford and zero gap on 6-7 lvl higer mobs than you are, and you will lvl very fast. Although not too fast when the 50's come around.. And I had GT the whole time untill PT's came out, then I swiched to them and Skill Tickets. Every little bit helps."
