Picking a comp and reading the lobby
Let your items and early upgrades point to the comp, scout who else is on it, and finish it once you commit.
Checked for patch 18.4. The numbers come from the live Set 18 data and follow every patch.
The idea
A comp is a plan, not a script. The best one for you this game depends on what the game hands you: the items you hold, the upgrades you hit early, and what everyone else is building.
Start from your spot. Your components and early pairs point toward a handful of comps that use them. Keep a few options open through the early game, then commit when one of them is clearly ahead.
Then read the lobby. Every player draws from the same shared pool, so when others build your carry, the copies you need are sitting on their benches. Boards on a comp nobody else in the lobby plays average 4.3; with two or more others on it, 4.8. Scout before you commit and again before a big roll. If several players are on your carry, pivoting to a comp nobody wants usually beats fighting over scraps.
Once you commit, finish the comp. Its carry has to make the board, and its core traits need to reach the breakpoint the comp actually runs. A board a unit short of a key trait looks nearly done but plays like a weaker comp: boards that short made top four 51% of the time, against 59% with the comp's traits full.
See it live
Play from your spot with the two components current comps ask for most, then what sharing a comp with the lobby costs, from ranked games of this set.
Comps that use both, best fit first

Flora Fatalis Azir, carried by Azir
4.11average placement
Lunar Aphelios Nidalee, carried by Aphelios
4.22average placement
Adaptor Master Yi Rengar, carried by Master Yi
4.34average placement
Average placement by how many others in the lobby play your comp
- 4.3
- Nobody else on the comp
- 4.7
- One other player on it
- 4.8
- Two or more others
Measured on this set's ranked games in HexKey, the same games the game review is calibrated on. A shared carry costs the same way: boards whose carry two others also built average 4.8, against 4.4 when nobody else builds it.
The rule of thumb
Let your items and early upgrades pick the comp, scout before you commit, and finish it once you do.
Check yourself
Using the line of average placements: what does a comp average when one other player in the lobby is on it too?
Pick an answer.