Ranked 5's

So my friends and I have recently been doing ranked 5's and I'd like to know how it works LP/Promotion wise. We were placed B4, when we hit 100LP we jumped to B2 no series. Hit 100LP again and went to B1 no series. Do ranked 5's have series or is it just our mmr? And how does team mmr work out? Because we recently faced G5 and then P5 teams.

Sorry if this seems basic. I'm just a clueless nut <3