Some ways i found of getting fast coins:

1: Buying with robux: pretty simple

2: Getting the pet: you can buy a pet for 75 roux and it will give you coins (im not certain whats the cooldown or how much it gives)

3: No Pay, Yes Gain, Repeatable: Basically go to World 3 on Hard Mode, play the game normally until you reach the stage "Dance Dance", its an easy stage BUT the catch is that theres alot of T-Pose Coins there, with hard mode you get x2 coins, so play the stage and get all coins (you should get 70) BUT dont go to the next stage yet, so now you can go to another world and come back to world 3. The coins will reset and you can repeat it forever until your pc crashes or something idk.

4: ooOoO Secret: There are alot of secret places in worlds and in them are usually coins. (i suggest using hard mode bcuz x2 coins) The most known are the rats. (to get past them buy the cat tshirt from the store for 10 dab coins and scare 'em off). I dont know every secret so i cant list every

i suggest using 2&3