mine essence, craft it into air and mind runes, buy a fire staff with that 2k of yours and start casting fire strike on the lesser demon on the uppest floor of wizards tower. for ranging, you could pick up the arrows in wilderness, near the bears north from the steel mine. from lvl 1-20 i'd suggest goblins in the goblin hut in lumbridge, from 20-30 goblins at goblin village, from 30-70 fortress guards at black knights fortress and from 70 to 99 kill lessers at karamja.