As you said you invested 50eth and you gain profit of 20eth? I dont know if you are in ROI of your money because you only gain 20eth and for me thats not enough to invest more because you are not in the ROI of your money. But if you are planning to invest more or you are going to invest your profit I suggest you to put all your money to an investment that you think it will 100% percent make your investment back or giving you more profit of your investment.