Hiya Lime and welcome! I am a relative newbie myself, been doing online dating since July and had about eight/nine dates so far. It's mainly been fun although there are some strange people about! I have been on various sites, started off on a paying one but am now on PoF as it got a bit expensive, and tbh I can't say I have noticed a real difference in the quality. Must say, I've not had any of the famous willie pics either . . .
You do get some strange messages, so the main thing to say is, don't feel compelled to reply. If someone just writes a couple of words, I never bother replying, and if it's something making inappropriate remarks about how I look I don't reply either. Beautiful/stunning/classy etc I can deal with, sexy is a non-starter for a first message! I might get slated for this, but I generally only respond to people with a level of education that matches mine. Didn't do this once as the guy seemed like a genuine person, and although he was, we were not at all suited. Weed them out by whatever criteria suit you, and don't be afraid to have a look round and message ones that you like.
Above all, and this is easier said than done (as you will see from my many wobbly posts!!) treat it as fun and don't get over-involved early on. It's really easy to do that especially if you've been messaging them for a while. If you are okay with what you hear after a week or so of messaging, go in for the date! It doesn't mean anything until you've met and can see what they are like in real life. (I've had a couple of shocks, one who was at least five years older than he admitted to, but tbh more good surprises than bad!)
Sorry, that was a bit of an essay 
. Do you want to return the favour and advise me about sleeping with people on Date 3??!! Decision has to be made tonight 