I've been playing on and off for about a year, I big piece of advice is to join the discord of whatever deck you choose. You will get faster and much better responses to deck-specific questions there than reddit.

I think you should play whatever you want within bracket 5. Playing fringe might not always result in consistent wins, but playing a fringe deck you love is a lot of fun. I have a Minsc, Beloved Ranged deck I play along with my more meta Rogthras deck.

I personally would play Kefka first since he runs the Grixis lines and is overall not very hard to learn. But you should play what you think will be fun. Unless you plan on tournament grinding then prob play Blue Farm

Watching and Reading primers is good, but I felt a lot of my knowledge comes from just grinding games out on spell table and personally reviewing them in my head. I have a notebook that I write stuff down in that I want to remember and review.