tbh, in my experience Killteam is a bit shit.
It uses the same rules as fullsize warhammer40k then shoves an unnecessary amount of extra rules on top, that make the game much more random and much less controllable.
In the end, killteam comes down way to much on dicerolls and thusly isn't as fun for me.
If you wish to stick to GW Products, maybe give WarCry a try? I played one game so far and loved it, they really thought about making a functioning skirmisher game here, opposed to an "Age of Sigmar LITE". The setting is Fantasy though, so maybe not your pair of shoes?
The models released for WarCry are also absolutely fantastic.
@Haino on the other hand, Infinity has had a new Edition recently (N4 if I remember correctly) they hugely reduced the weird nested interactions between rules and streamlined everything. They even have a "beginners ruleset" called "Code One" now, which works as a slightly reduced rulesset but with the same principles which you can use to learn the interactions.
I highly recommend it, as Infinity is in my opinion one of the best and most solid rulesets for skirmishers I know.