Maximize gathering time, minimize travel time. Ignore the Clouded nodes (unless you're going for the Unclouded achievements for some reason). It's only a 3 point difference between Clouded and Artisanal submissions so wasting time on travel isn't worth it. The Levin and Tempest nodes are fine if you are already right there gathering from the nodes on their islands. Flare and Duststorm are never worth it if total numbers are your goal.

Don't skip any nodes you see other than Clouded. It's also not worth it to switch between classes to first get mining nodes then get botany nodes on the same island. Both sets of nodes won't always be where you are.

Use your Auger as it charges. Never let it reach 5 full charges. Use it on the mobs by the nodes, not the lower islands (more time wasted to travel that could have been spent gathering). The Auger can account for at least 30% of your total if you're using it right.

Use your GP, don't save it. While using KY/BlH II on the +5 attempt nodes is the most efficient use of GP, those nodes are the rarest and hard to plan for unless you have their locations memorized. I use BY/BoH II once per node instead. If I happen to have 500 GP available when I get to a +5 attempt node, then I'll use the others.

Use your Hi-Cordials as soon as they come off cool down so you get as much GP as possible while you're in there (20 per hour you expect to be in Diadem).

Don't let other stuff distract you. Instead of watching YouTube, Twitch, Netflix, etc. while in there, turn on some good background music and keep your eyes on the gathering. Avoiding game chat is also a good idea.

Don't force yourself to do it all at once. Break it up over time. No achievement is worth messing with your sanity.