I also started with Kill Team. Couple months in, learned 8th was inbound, so I shelved it.
Got the rule book, the cards, Imperium Indexes, the special dice. Bought the Primaris marines out of the box set, and added a few vehicles and such. Have a 2K-ish pt army now.
I haven't been happy with the game, enough so that I doubt I'll pick up the SM Codex. (Although, the Primaris Chaplain is SWEET, so I might add him). Might just finishing painting up what I have and call it good.
Might let it continue to cook a bit, get some other codexes out, let the meta shake out a bit. See where it's at in 6 months or so, try a couple of the other stores in the area to see if there's better players/not so many direct counters to my basic Marine army, before I decide if I'm eBaying the collection or not.