Ranked Promo/Series

Have some questions about the ranked promo/series. Is there a better time to go through a new seasons promo? Is it better to promo at the kickoff of a season or mid season, etc. And What is the difference between the first ranked promo you go through after you hit 30 and each reset for the seasons? And How does duo'ing through promo series affect everything? If I duo with a higher ranked player will I be with mostly players at his level or mine?

Back story: When I first started and hit 30 it was mid season and a friend of mine went through promo at beginning of season. He is a night and day difference compared to me playing, he is much better. His win rate was better than mine and he got Bronze 1 and I was placed in Silver 3 with a 5/5 win rate. I steadily dropped and he eventually climbed. Last season I dropped hugely out of silver to like bottom of bronze with a 5/5 win rate again I think. I have two other friends who waited and went through promo later in the season, mid-late, and one got silver 2 and the other got put in gold(he is not a gold player even he says so). Have two other buddies who duo'ed together initially and got placed in silver 2 one not being a silver 2 player at the time and admits he was carried there. One of them has been playing a lot of ranked with some higher tier friends of his. How will this effect his ranked if he goes through promo with the other guy he originally duo'ed with.

Any advice or information about ranked promo and the details of how they work would be appreciated. With the new season getting ready to start I am debating on whether to go through the promo at the start or wait till later in the season. I really don't want to drop like last season.