People have been using coin not decrease, mana not decrease and no skill cooldown for progress with no notice of ban.
For farming relics, outside of tournaments you can just use instant max stage.
Farming inside a tournament is a bit different. At first you can't jump to your max stage. You need to first reach your max stage manually, and to do that faster, you can activate all item set bonuses. After reaching your max stage once, you can go back to use instant max stage jump.
What makes you get banned is going beyond what you actually can.
For instance, using coins increase will give you an infinite amount of money, and the game will recognize that you shouldn't be at a stage that goes beyond the money you actually should be getting and you'll be banned.