The best way for me is my way: Don’t pay for anything.
I build up my camp, as soon as events are available prioritize events before main story.
Event equipment is better.
Stay in Egypt long enough that your camp gets really strong (with event equipment) and enjoy cheap tile costs. Strengthen the camp further with 100 gem shop events. You get the gems with achievements. Play detective 2, excalibur and snow white in between the free events several times until you have all good equipment.
Use double material week for the green ring mines, use double production week for XP caravans.
I switched from clearing all to selective tiling in Scandinavia. Get to the best equipment (dragon eggs in China, hairlocks in Atlantis, shields in Greece). Leave the clearing for later, when you come back with a way stronger camp.
Am in the second half of Greece now, have never spent one cent with this account and my 40 min fast recharge is 32,000 per hour. So I have the 15,000 within 30 minutes.
I leave expensive tiles for first thing in the morning, that is around 160,000 energy with 9 hours.
Playing for two years in summer.
Edit: Oh, and I use the wiki to find the cheapest path through locations. End edit.
What did you spend money on? Never buy food. I don’t buy equipment, because then you have to keep on buying, as the non-pay-equipment is less attractive. But you can still quit buying any time. What is it, that makes it so „obvious“ to you, that one should spend money? Example, please.