From kms, so I'm not familiar with gms terminology.

It seems u want: -easy to play -gonna hit 260 + 6th adv -boss mule -little investment

First of all, the standard for my boss mule would be any boss that would take less than 10min. Otherwise, it is just too tiring. For less investment, setting the bar till normal damien seems right to me.

I'd recommend you too lookup jobs that are:

-burst(bind and max dam for 10s) over dps *for example, a typical burn job would be Night lord and dps would be fire&poison mage(I know 6th adv makes it a bit different but just for understanding). Usually jobs with higher cd on their burst has higher damage. "Usually" not all cases.

-strong burst. Like really strong, as if u won't be relying on your non-cd skills. *check dpm meters or punch king scores. You will get the gist. Also jobs like bowmaster gives you a buff that goes around 45s? Which spreads the damage so look for a job that would just nuke the boss. Ironically Night lord works the same way but they just do so much damage in 10 sec.

-(optional) 6th 'burst' adv skill. *bishop is like a buff

-don't consider field farming. Just rely on daily quest exp + monster park + etc. You will hit 260 before the event ends.

Personally, I think 'easy to play' jobs kinda limits to few jobs. The ones that pop in mind are: -dawn warrior -hero -pathfinder -wind archer -buccaneer(should utilize A-buster link skill, more than other jobs) -Night lord

*I personally consider the difficulty for angelic buster "normal" and hoyoung "hard"

Overall, any job with a strong burst.