A few tipps for beginners
Spezially at the beginning you have not much room for Fighters, and you have not much Money. So let the fighters in the Heists and spend so much money as you can in your Town
Build Watertowers and level them up to maximum of 4. When you have reached the 4th Field start to build Pubs in Field 4 and 5. Then when you can buy Field 6 start to build media stations. Sell the watertowers and build there Media Stations too. Do this because after level 50 you will need 1,5 Hours to fill your energy, so its sensefull to own Mediastations. They Produce less money per Hour, but they can hold more after 90 Minutes than the pubs. When you have Buyed field 7 and it is filled up with Media Stations sell your Pubs and build Media Stations too. All Buildings except the 3 level 5 Buildings from the Quests you can sell.
But Be Carefull, when you have more fighters in the Heists than free Places i dont know what happens. So if you need to open and you have not enough money. Spend the first Wave of fighters in your Choosen UC Team (More about that later in the text) this will cost only 1600 Coins for 8 Men, means you can Drop 80 Men in 10 Fighter for 16000 Coins (as Example 4 Yukis, 4 Master Jades, 4 Grandmaster Yong, 4 DR Saiphoon, 4 Mirelda, 4 Kai´s, 4 Elises but only if you want to Train them, and only one fighter of each element)
As startup it CAN be usefull to build a 4 Fighter Maxed Common "C->4->UC" , he will have Values about 500, this is to less for the Gaming after Level 50 and you will delete him, but for the start it is an idea, Spezially "Erin" is a good Choice, he drop Often in the first 30% of the Game. But this is something you CAN do, not you must do.
Begin so early as Possible to build a Team of 5 "UC->4->R" Fighters, one of each element. Mirelda, Kai and Elise would be an idea becacuse they are Part of the story but they have a big Disadvantage, you cant get them by Fights, you can obtain them (Nearly) only by Heists. So bether start by Train Master Jade, you need 66 Earth Common fighter to max her First time, and you need by using the 4 Fighter Formula to do this 7 Times, means you need 462 Earth Commons, a few less because if you Farm them at Earth Temple you will get more than your 4 needet copys of Jade, And to Train Jade with Jades has 2 Bonuses, UC bonus and the Bonus by Leveling a Fighter by the same fighter, so i Think you need around 400 Fighters. Jade should have now around 900 Points. With her you can now start to Level a Sable at the warf (Or Kai if you have 4 Copys), Jade should be able to clean all 5 Levels of the Wharf alone. After that you have 2 "UC->4->R", Because Water Temple is a bit to Hard for 2 900er Fighter you can Choose level a Borvo, Grandmaster Yong, or Elise at Fire Temple, or Train a Yuki.
Finally you will have 5 Fighter, one of each element, you should play now for the second or third week (or (much) longer). So you will have now more than 2 Rares with more than 4 Copys.
So Start now to add to your 5 "UC->4->R" two "R->4->SR" with the Bosses you Killed
After That you can attack each Area or boss With a Full 6 Men Team and leave the "UC->4->R" Fighter with the Doomed Elemant at home. If you build 3 instead of two "R->4->SR" you are able to attack the area without doomed fighters.
From There on its Luck, you can open each week 13 Premium Heists, and you can only Level what you get from There, i play now for 3,5 Weeks and have my First "UR", on the Tablet of my Sister i Startet Last week and now i have 4 "UR", 2 of them are Gwens.
The 4 Fighter Formula is fine for your Startup Team and its fine against Bosses and for Farming, only in PVP the 8 Men Formula makes more Sense, finally only 1 more point in Speed can decide the Fight
Hope this help at the beginning
Ahh and before i forget it, if you are not able to Max your Fighters before you Fuse them, Stop to Play this game, you will !!!!! NEVER WIN !!!!!
When you start, begin early to loet the trucks closed, You have spezially at the beginning not much room for fighters. So its sensefull to use your money not only to train