you have to set some rules for yourself. Buy a coin, wait until the price goes up at least 100%. Next, sell your initial investment and invest it in another coin and repeat.
For example: buy $50 XVG, when value goes up to $100+, sell $50 XVG and invest in a new coin, f.i. Neblio. Don't touch XVG after that point but focus on the new coin instead. Once Neblio hits 100% profit, sell half and put in a new coin.
Once a month, have a look at your portfolio and decide if you need to sell something or keep.