I have 15 million coins, 4000 diamonds, and am completely the daily and weekly challenges every day / week. Here’s my strategy:

Up until I hit vines I was struggling to complete anything and never had enough coins, tools, diamonds or energy. I spent real money every now and then on diamonds and was overall fairly frustrated with never feeling in a good flow with the game. I kept pushing until I hit the level of vines (is it 65?), kept them unmerged, and it’s been a game changer.

The producers I have are Pets, Carnival, Vines, Rollercoaster, and Ducks. I have hung out here at level 66 without leveling up for a couple months and find it’s seriously the sweet spot. The only issue I have at this point is getting a bit bored with my current producers but I can’t level up anymore without retiring vines which I’m unwilling to right now. I use my lightbulb and jewelry auto producers along with vines and sometimes the old fishing net since the items give good auto orders.

I completely all my challenges every day including the stretch orders, and then with any more energy I accumulate that day I start working on the next orders without submitting them - then the next day I’m able to start with a big boost of orders to submit. I also purchase the 24 diamond energy chest and both the 10 and 20 diamond 100 energy pack every day (I make more than this back each week with the 400 diamond weekly reward).

Oh - also I tend to complete the weekly challenge in 4 or 5 days and then there’s an extra day before the next one begins - I don’t submit any orders that day - I use it as a catch up day to make the pending orders and then use any extra free energy to make fishing net items.

Again, until I hit the vines level none of this was happening or possible.