I started about four and a half years ago having read a few posts from a keen online gamer over at a set of UK AWP forums. (Bear in mind I've been a UK AWP player for over twenty years, and for the last decade or so, a somewhat successful one, so I figured I'd be able to do well on online slots too
)
So I jumped in with both feet, having no idea whatsoever about how RTPs or variance worked, about matching your stakes to your bankroll, and so on.
A couple of early 'highlights' were losing £500 in about 30 minutes at Kerching playing a Monopoly slot at £4.50 per spin (that was 5 x £100 deposits, and triggered a call from my bank's fraud department the next day), and a absolute headfuck of a session at
32Red where I lost £1000 (!) in an evening whilst Mrs Chopley was out and Chopley Jnr was in bed. I finished off playing some single line slot at £3 per spin and watched every last penny of a £1000 deposit disappear.
To say that I had trouble sleeping that night would be a serious understatement.....
After about £3500 of losses across various casinos and softwares, I actually did a little bit of research and realised where I was going wrong (playing stakes far too big relative to my bankroll and/or hitting high variance slots and not understanding that RTP takes thousands of spins to make itself felt on random slots) and thereafter I did a lot better.
I do also remember a very good early win at Jackpot City on Summertime (the Thunderstruck clone) where I hit 5 scatters in free spins, which was my first win over 1000x stake (IIRC it was around £1100 from a 90p spin for the entire round).
My early horrible experiences with online slotting are part of the reason I still get so hung up on RTPs and variance and the opaque nature of online gambling in general, because an uneducated player can very easily lose large quantities of cash in a very short space of time.