The deposit requirement is $15 (in any form of crypto available not just Mbtc, you can still use Trx which is cheaper) and you only need to spend $1 for any spin before withdrawing all your winnings. I'm used to Trustdice and indeed for those just starting out it will be a bit surprising but in fact it's not that difficult. For example, at that time I wanted to withdraw $180 but because I needed to make a deposit to fulfill the bet with a minimum deposit of $15 but you only need to throw $1 in any game, you can immediately withdraw the entire balance you have. Spend $1 in as little as 10 seconds.
Your explanation and example is not what is mentioned on the terms (5x wagering for the 1st deposit). How can you say you need to throw away $1 only if the first deposit is $15 while mathematically you need to wager 5*15= $75 in order to be able to withdraw? It means that even if he bet all his first deposit in a single bet and win, it is still not enough to withdraw because of the 5x wagering requirement. I'm not pretty sure but I think you are talking about non first deposit so you can withdraw your money immediatelly after placing $1 bet only.