Well, when you buy those shitcoins you are taking high risks which are compatible to the potential profit you might make with them, since you talked about 300%-500% and even 20.000%. Therefore, you can expect it's not an easy thing to do, or even something sustainable to keep doing on long run in order to increase your portfolio. Better to stick to solid cryptocurrencies which won't be delisted from exchanges, even though they don't have the same profitability potential of shitcoins. And if you are still willing to be greedy, make sure to use only small sums of money to acquire those shitcoins, as you were gambling with your money, and not exactly investing it. After all, these shitcoins can't even be considered investments due to the lack of fundamentals behind them!

But who knows... Maybe you can be really lucky to turn few bucks of dollar into few hundreds of even thousands if you pick the right shitcoin on the right moment, before it's too late and it starts being dumped by the speculators or delisted from the exchange. In every cases, your profile of investor will determine if it's going to be a good deal for you or not. For conservative investors it's definitely not, but for risk takers, it might be an option.