Been running a non meta build and having lots of fun and success right now. My rank is still quite low but it's nice to have found a fairly consistent build that's been leading to high placements. My build is pretty simple load up on knights, get guardian buff, stack items on Poppy. The items have been pretty consistent to acquire, need a Thornmail (2x Chain Vest) and then a Dragon's Claw (2x Negatron Cloak) and then I have been trying to get a Warmog's Armor (2x Giant's Belt). Not sure if Warmog's is the ideal third item but it's been pretty good so far.
I've been toying around with what to use after getting 4xKnight and 2x Guardian buffs, there isn't a ton of wiggle room but you can sneak in an extra buff or two. Depending on how the early game goes, you are usually forced to go all-in around level 7 or 8, longer you can hold out on going all-in the better. I've had most success with adding in a second Phantom for the buff and occasional instant kill. Karthus puts out pretty nice damage and can be a nice sink for any extra items you might have. I also like trying to build a tank dps alongside Poppy (or whoever you dump the thornmail, dragons claw on). Lockets, Titanic hydra, statik shiv are all pretty helpful in whittling down the opponents HP pool before they all kill themselves hitting Poppy.
I hope I can keep using this strategy for a while and move up the ranks a little bit. Been loving TFT lately and it's pretty much been the only game I'm playing on my PC right now.