This is my personal opinion on the best way to go at the game that I have figured out from info gathered from multiple sources, mind you I have no way to confirm if some of the given info is true or false so if you see something that is wrong PLEASE let me know!
First thing you need is Sidekick, this tool is EXTREMELY useful. Once you have it started go into the config and set it to "Coins", this will make it rate the missions based off of coins instead of XP.
Boosters, I can not stress this enough but ALWAYS have the 10 Doughnut -50% Mission Booster, lower E cost for Missions means more Missions and that means more chances to get Items/Doughtnuts. The other 2 you can use the +25% one.
DO NOT Use the Free Store Refresh until AFTER you have used all energy for the day, the Stores Items are based off your level when you refresh it so waiting til you have leveled all you can for that day makes more sense.
Ok, that is the basics covered. Now for the proverbial "Meat & Tatters" of it.
For Missions I highly recommend going with Low XP/High Coin Missions, the reason for this is the more Coins you make means the more you can buy Stat points. The lower the XP means the slower you level which makes you tougher for your current level.
On a side note Missions that have items are NOT a bad thing, if they require only 2-3 E to complete you can always sell the item if its not a upgrade to your current equipment. Doing that increases the Coin value of the mission greatly but its not always guaranteed to work due to occasionally the items sell for VERY low Coins
Energy refills are a MUST, for the first 20 Levels I do not recommend using the 3rd and 4th Refill due to the cost. This is completely up to you though. After level 20 using all 4 Refills is highly recommended, wait until you have none or 1-2 E left BEFORE getting the 3rd and 4th Refill, the reason for this is I have heard from multiple people that the 4th E Refill offers a INCREASED chance of getting Items/Doughnuts from Missions. (Any Developer want to Confirm/Deny this please?)
Once you have bought all of your energy refills and refreshed the store all remaining coins should go to buying and increasing your stats, for stat buying and free stat points I highly recommend keeping your stats even and let your gear alter your stats to give the build you want.
The best PVP Build in my opinion is Strength 15%, Stamina 25%, Brain 30% and Intuition 30%
Another amazing build is Strength 30%, Stamina 40%, Brain 30% and 0% Intuition. (Thanks Test12!)
Well this is all I can think of so far but I will add to it as people offer ideas and I figure more of it out.
credit = devarmaya