How does Ranked work?

Ill start this off by saying I dont know if this is the right place to post this but the categories arent very precise. OKAY so I started playing ranked recently and started in Iron IV. I won 6 out of 8 of my first games and Ended in Bronze IV (I think), and after that I kept playing more and more and once I got to Silver 4 100 lp, I won my next game and ended up in Silver 2? It just skipped over silver 3 altogether. Then after that I got to 100 lp silver 1 and skipped right to Gold IV. No promos or nothing. I just finished my 100 lp game in gold 4 and now Im in Gold II. Why am I skipp ALL my promos and 2 whole divisions? Whats the dealio riot. Side note, Why am I always the lowest ranked player in ALL my games, I played against 3 platinum players when I was gold 4. Theres no way thats supposed to be how it works. anyway please let me know why all this weird stuff is happening. Sorry if its confusing, English isnt my first language ._.