I think for the first capital that you might be able to do to start trading you must have at least $ 50 of capital to be able to use it to buy some coins that you can do to grow assets you can, after having bitcoin then you can use the bitcoin you have to buy altcoins that are still very cheap and enjoy the benefits you can get.
It is your choice how much do you want and have to invest, but it is good to start from low investment because if you lose your money due to fall in the price, you will not be too much disturbed and will be able to recover your deficits easily. If you lose bit money then it will be difficult for you to recover. Anyway there is no limit for starting cryptocurrency trading.