Should i try to make a website and invest in this or keep it as a side hustle?

So i(22M) while in college have started to sell custom plates for decorations purposes in my country and i have made about 300-600 € monthly while working about 6-8 hours a week from them . I have had thoughts of making it official and selling them worldwide but i will need to invest some money to promote and for packaging.
I work alone for this and i make them for 4€ while selling for 15€ and i see some potential but at the same time i can see how it will fail . What is your advice , opinion?