Puts you in the top 25% of players according to Lol wiki (Here) but take that as you want. From my personal experience my rating started about 1300, went up to 1459, then I had an awful run of games losing 13 of the next 15 and a fair few more of the next say dropping me below 1200.
I've managed to even out my win losses at around 1300 but I think my understanding of the game has improve drastically since I started playing ranked so i'm hoping it'll go up over time. I would say to get a precise reading of your elo you'll probably need upwards of 100 games but to get it within a near enough range 50 or so should do.