The bigger your bank roll, the quicker and easier it is to make money.
The quickest way is to do the sign up offers. They are the easiest and most profitable and are great for building your bank.
I personally recommend avoiding casino offers until your bankroll is £1.5. It isn't a case of play slots and hoping for the best as every casino game has an RTP, which is their return to play percentage. A good slot will be 96% which means if I play £10, 10 times, probability tells me I will walk away with £9.60. The only way casino offers are profit, is when we are getting something back. And not ever offer is positive EV.
There are plenty of guides on oddsmonkey (recommend joining 100%), but they aren't risk free and you can and will lose money and until you have a steady income from MB and bankroll, it's more risk than it's worth.
Sign up offers are the best way, so crack on with those, there's easily £1000 of profit from sign ups. Once you've finished the sign ups, hopefully your bankroll will be around £1k, by this time, you can definitely make £100. With a couple of hours a day, you could do £500 a month once you've got the hang of it.