Don't forget the bonus on the Multiply BTC game. Freebitcoin regularly offers to the players free coins bonuses to wager on this game. I don't really understand how much you need to wager to get it and how the amount given is calculated but it greatly reduces the house edge when you're gambling it, because you still get RP points and lottery tickets for what you're wagering while the coins you gamble are free.
The bonus you are talking about isn't really free.
If you claim a bonus, an amount equal to the bonus is deducted from your main balance and the deducted amount and the bonus goes to bonus account. For the bonus balance being credited to the main account, you have to wager the bonus balance 25 times. Given the 5% house edge, it's expected that you lose the bonus completely and 25% more.
Yes but you can choose the amount of bonus you want to get, you don't have to take it all. So for example, if you planned to wager 0.1 BTC in the coming week before getting the bonus, you just need to take 0.002BTC from the bonus offer. At the end you will have wagered the 0.1BTC planned and received 0.002BTC. It's maybe not very interesting for people who don't like to play dice games, but if you like this game, it increases your RTP.