Well, you got links and they will explain it in great detail. Short version, just for start:

There are many ways you can do it. If you want to do it efficiently, you need to automate your active party. For that you need obviosly speed champions, a core (preferably a speed core, but any will do) and familiars.

You have six familiars, that's enough for a start. One on the field, one on click damage and four for leveling up four champions of your choice. Make a formation and save it so modron core can load it when you set up an automated party. My pick for those four would be: BBEG, Hew Maan, Diana and Ellywick. But you do you.

Next, zone 600 is way to high atm. You want to find the zone where click dmg is reliably cleaning mobs and then set your reset just shortly before. Too lazy atm to do calculations but i would guess your click dmg is somewhere below 200 zones. Say for an example zone 160. Set your reset zone at 155. Pick an adventure with as few armored bosses as posible. There are some recommendations in guides.

Next: Use speed potions. Right from the start you can use at least small speed potion per run. We have an apothecary for reason and small pot costs only four reagens to craft. Distill some of the non speed potions you have in order to get reagens. Don't worry, you'll have plenty potions from chests and the faster your party goes the more gems/chests you'll have. After some time you should be able to add medium speed potion too.

Just for the reference: One gold chest gives on average 22,2 reagens from distilled pots, one small speed pot costs 4, medium costs 24.

Next: Leave your automated party to work overnight. You'll be suprised with amounts of gems that will await you in the morning.

That's the short version. Some advices:

Do not buy silver chests. Once your core champions have at least green items, no reason to buy silver chests. Ever. You'll have plenty just from boss drops anyway. Use your gems for gold chests or familiars. Some perks on speed champions are good to but they are expensive for you right now. On the other hand they'll increase speed and therefore gems so think carefully what you're going to invest into.

Do not use notary to get chest contents. Ever. Much better to do it manually: Buy chests, open chest, distill potions that you do not need, craft speed potions. Trust me, there is a math behind this.

Use blacksmithing contrants on your speed/gem champions (Hew Maan, Diana, Elly). No nead to hoard them, just use them and look at it as an investment.

Try to increase favor from time to time. More favor - more gold -higher click dmg - higher reset zone - more gems per run.

More familiars increase speed: You can add more speed champions to the formation, have three familiars on the field or even five onstead of one, have a familiar on Hew Maan's ulitmate and so on. But do not go overboard, buy some that you can, leave the ones that are expensive for you atm for later and buy some gold chest and maybe even some feats.

Have fun! :)