The only strategy that is "cost-free" is being the house for a few years. As long as you keep trying to be a player, you will continue incurring costs, and the more you search for it the more money you will lose trying different ways of doing the same thing: gambling.
I got lucky once too like you did. Many years ago I accidentally bet 5m satoshi on a slot machine. I thought that I was in play money mode and figured I'd empty my balance out so that I could refill it, but it turns out that was actually real bitcoins mode, and that was all that I had at the time!! By some turn of fortune, the reels came up with matching symbols, and the machine spit out 25m satoshi! It was only worth about $30 at the time, but that win made me feel like the only way I could go was up and I kept gambling and gambling for months. That was a mistake, and I hope that you realize it sooner than I did.
I'm feeling exactly what you wrote. After winning 3.5M sat from only 60K sat, I was so addicted to the game. Even I played it while I'm on my date. I think system marked me for too much playing. And that's why I lost everything.
For the information, I bet on 'HIGH' for 19 times gradually increasing my bet to double and everytime it fell for 'LOW'. What do you call it..?? I think it's not luck..
It is luck. You go up, and up, and up, and the longer you go, the higher the chances of you eventually failing is. Just because it is improbable to lose doesn't mean that you can play over and over again with the same risk of losing. The more you play, the more likely it is that you will end up with a losing streak eventually. This property applies in reverse to bitcoin mining. To solve a block you need its hash to begin with a certain number of 0s. You can try it, and you will most likely not succeed. But if you try quintillions of times per second, like mining pools do, all of a sudden it is much more likely that you will succeed at least once. With gambling, the more you play, the more chances you have to lose everything. Just because it happens eventually doesn't mean it was rigged or you were winning too much. It's just pure probability.
You have to escape. Get out of gambling before you start betting what you can't afford to lose, or else all of your money will constantly go into that hole that is the casino. Every paycheck you get will go straight in there because you think you can win. And when you do win, you still lose everything by playing with the winnings, because it wasn't enough to cover all your losses up to that point and you wanted more, or because you just don't know when to quit. If you quit gambling before it gets to this point, your life will be all the better. I have seen too many friends who couldn't quit at this stage when playing with satoshi and went on to throw away what I make in a year in one hand. Enough money to put them through college, just gone in one day. This isn't just one friend I saw do this. It was a few.
There are other ways to get bitcoins. Gambling is not a very good one.