You haven't taken our pearls of wisdom onboard yet?
There is no 'method' to the madness with slots, or else we'd all be doing it.
If you have a healthy starting balance (£500 - 1000) you just adjust your bets according to that, say 80p - £1 bets or so and see how that goes.
If you have £20, you bet small like 20p (or less!!) and build up the balance if possible.
Important thing is to set yourself a cashout target before even starting. If you're happy to make a £200 profit, then stick to it. Don't get too carried away in the moment and don't go crazy with high bets.
There are those that would 'just go for it' with a £1000 balance and start doing £5+ bets from the outset. If you're going to do that, be prepared to be likely out of pocket, very quickly!