I'm quite low leveled at the moment, but I find the best way to level up quite quickly for the constitution and strength and defence levels is fighting level 11 highwaymen, there is also some level 18 guards I spotted yesterday although i forget the exact location of the guards if anybody knows the location of them do share below I believe its in Asgarnia somewhere, I can share where a good spawn location for highwaymen is, they can be found in between the white knight camp and the clan camp, just by the side of the mining area that is next to the white knight camp.
Hope this helps new members to level up
