In order not to lose your entire deposit, you do not need to open an order for 100% of your available funds. Actually, there is a risk management strategy for this. Try trading 2-3% of your deposit. In this case, if the price moves contrary to your expectations, you will lose only these 2-3%, and not the entire deposit.
Well if they start with only 100$ then this method would mean spending 2-3$ per trade which is literally nothing. Therefore proper choice coins before starting the trade is important. The altcoins will always lead to bigger losses but not bitcoin, so that is one point. Again knowing how to deal with a opposite side movement is also important. Here you don't give up hope and panic sell but you hold it so that when the price crosses over you can sell the asset to break even.
However these little things will never be learnt from signals groups and all. It comes from practice and experience.