Thanks @ridoskon - you’ll probably be aware that there are means to extract +ev from CFDs, and sports betting. Donglemouse was a well known poster on another forum that made 100k from such offers, but alas the process is so well known that bookies and spread betting companies have become a lot smarter. They are now more active on users taking advantage of account offers.
I was an early adopter, but sadly I used the earnings to supplement my income at the time, rather than seeing it as extra income that I should have invested.
Bonus bagging can still be done to an extent, but back to CFDs and spread betting, normally the margin is high to the point that unless you are extremely lucky or good at predicting movements (or +EV odds), then you will lose long term.