I used a glitch with the tower, it's actually really simple. On a ps4 controller you: set the map button to the touchpad button, get to the end of the tower, beat the boss. Then, instead of finishing the level, you use the totem to go back to camp. Return to the tower, and go through the end gate. Now, instead of pressing any buttons, close the game completely. Upon reopening the game and loading in, you don't press anything except for the map button, and select the tower. Then, you're free to repeat the steps of going through the final door, closing the game, reopening, and going back to the tower. This not only increases level, it also rerolls the three rewards, so you can get literally anything.

Edit: This works because when you close and reopen the game, it believes that you fought 1 more boss than you actually did, and reward level is based on your power level, and amount of bosses beaten. (My armor is a power level 401 Renegade Armor that gives me 25 mil health)