With the casino new customer offers, I didn't come out with any profit at all, but I think the offers the casinos email existing customers are potentially more profitable. It is difficult to decide whether they're worth doing or not, with the bonus amounts, free spins and wagering to consider.
Personally I just punt what I can afford to lose on offers that seem good. So far I have lost £10 and £20, but I also punted £20 and came out with over £600, so it can be done! At the moment I am doing some daily spins I was awarded at two bookies, I have about ten pounds winnings on each right now, but I am doubtful I will get through the wagering unless I have a big-ish win. But you never know! As I say, only punt what you can afford to lose and don't get swept up and be tempted to chase your losses.