That amount is quite a lot for me too and I think it's very difficult to get a win easily especially like that, but I'm amazed you have a bet of 1500, that's quite big for me.
Rp800 is basically small amount but of course it is about our own preferences, no doubt about it.
If Rp800 is still too big for you, you can play at other casinos and play pragmatic games where the minimum bet is still allowed at Rp200/250.
However, if under 800 is still too big then I think you should not even gamble at all especially for slot game.
Maybe other games where you are allowed to bet less than a single cent will be the best games for you to play.