I want to do DCA, what should be my limit order size so I can cover the current -50% loss?
One of the rules of trading is to never find a way to trade and gain back your losses, this is because it can lead to you having a kind of thinking that will make you to open position when risky and not necessary and resulting to more losses, this will later make you to be more vulnerable to losses until your total funds are gone.
With what I can see, you are still not good in trading, do not leverage, and do not try to increase your leverage. The more the leverage, the higher can be the gain or loss, but as you are still learning, do mot leverage as learners are vulnerable to losses. Just open 1x which is enough and learn more about trading.
The money you lose is gone and let it be a bygone and focus just only on and only about how you will gain and minimize losses and having a net gain. Use the amount you can afford to lose and learn more and have more experience.
Lastly, if you do not leverage, notice this, if you are losing, just do not close any position, it will surprise you when the market will reverse and favour the position you opened. Many newbies lose because they close position when losing, that is not trading but gambling, but can be used for leverage trading by experts, but if you go 1x leverage which means you do not leverage, do not close position while losing and e hopeful for a reversed market trend.
I will advise you to only use bitcoin for now to learn, altcoins are more risky, shitcoins can result to losses even for expert traders.