Using martingale in trading? Hmm. Not a bad idea but you have to be careful at picking what altcoin you will invest with. There's no assurance that every altcoin you invest with will make a 100% profit so you need to consider that too.
But as a gambler though, we all know that martingale might not work because you really need to be lucky and at the same time, deep pockets to double every time. So very hard to maintain this kind of settings specially for altcoins.
I am not against this kind of strategy but like I said, you need to be careful at picking another altcoin because there's a chance this could all go south and every profit you made from the first, second, and the next to it will be gone in just one sweep. You don't want that to happen.
If I were in your position, after making such profits I'd rest and put it in a reputable altcoin like Ethereum or other top rank coins in the market. That way you can assure that the value won't go further below although the increase will not be that much in just a short span of time.
Even if you are still very careful, things might not go against you, and after that all capital being sweep in a blink of an eye. Perhaps this strategy is not going to be effected at least in altcoin trading. Just pick one altcoin or just bitcoin and then accumulate as much as you can and then HODL. It's not as complicated process as what the OP wants.
Anyhow, best of luck to him. Trade at your own risk.