Maximize this bonus. I'd like to understand if my strategy to maximize this welcome bonus is mathematically correct.

A bookmaker is offering a bonus of €50 to all its new users after they deposit for the first time on its website.

There are some rules:


Before you are granted the €50 bonus you have to bet at least €50. This could be done cumulatively, e.g. you could make ten €50 bets or just one €50 bet.
After you get those €50 bonus you have to bet other €50 before you can cash out.
Every bet you make has to be at least 1.5 decimal odds (EU), e.g. if you bet €50 you get €75.


My strategy is based on a few thoughts I've made:

Since the bookmakers get a commission on each bet it's better to make just one €50 bet to get the bonus and just another €50 bet to be able to cash out.

At the same time I would choose an event with the highest allowed probability to happen (1.5 odds).

Do you think this strategy correctly maximizes our expected value?
Theoretically speaking,

a) The amount you bet does not matter, as long as the money you can win and it's probability are all in proportion. For example, there is no difference in betting \$1 or \$100 on a dice roll, as long as the winning amount is \$6 or \$600 respectively.

b) Each win or loss has no effect on the next bet.

c) You should never bet if the opponent can win more easily than you. So if the bet is fair, but an additional commission is being taken, you are at a losing side and should not bet.

If these rules are followed, you should make only 2 bets of any amount (it doesn't matter). Then again, if these rules are followed, anybody betting in a casino is at a slight losing edge due to the commission paid.
Theoretically speaking,

a) The amount you bet does not matter, as long as the money you can win and it's probability are all in proportion. For example, there is no difference in betting \$1 or \$100 on a dice roll, as long as the winning amount is \$6 or \$600 respectively.

b) Each win or loss has no effect on the next bet.

c) You should never bet if the opponent can win more easily than you. So if the bet is fair, but an additional commission is being taken, you are at a losing side and should not bet.

If these rules are followed, you should make only 2 bets of any amount (it doesn't matter). Then again, if these rules are followed, anybody betting in a casino is at a slight losing edge due to the commission paid.