GR 70 is pretty easy if you have correct gear. You don't need any ancients (ancient weapon would be nice tho - this is ur first goal in terms of ancients) and you definetly don't need any augments. You just need correct items for the build you are using. I'd pick some build that is high rated on diablofans and gather stuff for it.
For "easy" classes that can reach 70 without problems i'd go for: wizzard, crusafer, nerco. I mean those i have some experience with, so i dunno how easy are wd and barb. I wouldn't recommend monk for that task. I played it some time for 1 season and i felt that its much harder to reach 70 with monk than with others.
Some tips: don't try to clear all mobs, leave single mobs and focus on bigger packs. If you see that some packs are dangerous and you can die multiple times on it, its better to skip it too, else you wont gain any time if you keep dying. Classes that are heavy cc dependent like crus or necro should skip most of juggernaut elites too.