Of course, buying random coins is a big risk because there is no trust on the project that it will survive the market and give you good profit in the long run. Bitcoin is very promising as long as you only buy and hodli for lonh without chasing short term gians. Altcoins are for short term, and the moment you see profit, its better you sell and take profit. They are not reliable overtime.
Maybe some technical buying random coins how to get opportunity to earn profit with any difference coins, its looks old trading technical when remember don't put eggs on one bracket and most of trader buy several kinds of altcoin.
I think most important but one or two coins but have potential and make research before buying, wait on the right time to buy and always priority with top altcoin at CMC without buy any random coins and don't make research yet.