I understand the first time deposit will be a confusion for all the online casino players here, by sharing my own gameplay experiences. For the first time deposit i will look on the casino promotion first. For the first scenario, let say if i found there is any specific promotion example like setting up a deposit target to trigger a topup free bonus then i might add on a little more credit to hit the target in order to trigger the promotion free bonus. Some certain platform might provide mobile top up discount to encourage more mobile user to join the casino games. So you might try for that way if you are interested to earn more bonus while topping up your online account.
For the second scenario, let's say if there is no free bonus promotion then i might just top up for a hundred to test my luck on that casino games. I will only top up for more if i see there is a chance for me to win more, top up wisely is a very important point and you must make sure that you are able to control yourself, make sure you don too addictive to spend on the specific online casino or else you might lose all your money within a sec.
Besides the first time deposit, i might ask you to consider about this. Only topup for certain casino that with high authority. Authority Casino like Livemobile88 or Ali88win will be the example that i suggest you to refer on. You can check a casino's authority in different ways, survey casino player's feedback is one of the useful tools here. Or you can also refer on their topup's testimonial like just to make sure that there are actual casino players who willing to topup on that casino platform.
Hope my suggestion might help you here.