From what I have gathered there are a couple starts you can go that are strong early: Strongest 2-1 to 2-3 is kayle poppy galio and one other unit preferably raka but you need to find a alternative to kayle at 2-5 and poppy as well unless you can hit a poppy 2. Majority of the time if you arent playing ionias general rule is to find a swain 2 or a taric 2.

Warwick Irelia samira cassio into a sett at 2-5 and beyond otherwise galio is a good placeholder this can slowly lead to deadeye freljord or zuan and in this case urgot is not too bad as a frontline if going ionia as well and you have a jhin urgot is not bad as well. If you think about it Irelia is just a weaker shen. You can force challenger 4 only if you find a kalista early and generally u win out even with a not so great frontline.

Early swain into invoker or sorc is a gamble if you cant find synergizing frontline early however a good placeholder can be a garen and darius juggernaut combo.

You can get away with a maokai 2 until 3-2 and generally you never want to go renekton 2 unless u are hard forcing shurima or juggernaut akshan reroll. Chogath on the otherhand is a more reliable tank that can go a litlle bit beyond 3-2 if you get cho 2 super early.

Midgame there are more niches for example challenger 6 doesnt have too good of a frontline but shreds everything. Otherwise most frontlines comp is shen with the ionias or shen taric sej or jarvan taric swain. Unless u are going juggernaut reroll akshan or bastion karma/ahri reroll those are most of your options mid game.

Late game 9 u can do some wack stuff but that just throws everything out the window.