In my opinion the biggest mistake you are making is watching newbies on youtube who pretend to be "experts". Such videos may get you some basic ideas but they are terrible for decision making. You have to watch the market itself and most importantly look at the charts. Just zoom out and see how each altcoin has been performing over the past years (not just couple of weeks or months). That gives you a better view on whether bag-holding altcoins is a good idea or now...