PSA: Pre-made builds are just suggestions, not requirements
Now at some point or a brother, you've all seen that one person who absolutely never deviates from the suggested build path on the item shop
The kind of person who builds full armor against a team of full AP, the kind of guy who only builds crit instead of even some armor pen against a team with 3 tanks
It turns out, you are technically allowed to purchase any items you want as the game goes on, and in any order as well to really suit your current match up
Please note I'm not saying just buy any random items you want and expect it to work, like building full tank Janna
So please, feel free to experiment with the many items available from our friendly shop guys who may or may not actually be friendly, and see what items you could buy earlier on to really help you out instead of always rushing that B.F Sword or Rabadons
(Small example, be losing lane badly in the bot lane and buying a vamp scepter cuz you're against a poke lane and forced to back constantly so that small life steal can help)
OR MAYBE BUYING A GAT DANG EXECUTIONERS WHEN YOU'RE LANING AGAINST MUNDO OR SOMETHING INSTEAD OF FACE TANKING HIM CONSTANTLY AND THEN RAGING ABOUT HOW OP HIS PASSIVE AND ULT ARE
This has been a less than helpful example of stuff you can do, now go forth and continue to feed win games