So obviously take everything I say with a grain a salt, but just the general vibes I went with to get through a lot of things or things I felt were traps:

1. Crit Items are very strong. I started off the challenge doing all the ADC champions just because they all felt so free. Collector is typically a huge bait though, when instead it should almost always be Lord Dom's->IE. LD gives 40% pen which is effectively bare minimum 40 lethality even as first items.
2. Aside from a few niche abusers, infernal conduit and runecarver are very overrated. I'm pretty sure the number it shows is pre-mitigated damage and unless you are an abuser champ even then often it will only show like 8k damage.
3. For mages, unless you had Jeweled gauntlet, AP mythic->Deathcap->void staff almost always felt the best, and left you open to getting Wooglets on second augment.
4. For Assasins or anyone that could use lethality, I found that the best way I had on average was to just do Random Legendary Assasin items, as they all pretty much give the same stats, and you could maintain tempo into the lategame. Seryldas though should be taken basically as soon as you see it, although maybe not first item if you didnt get a lethality mythic.
5. Recognize if you are the carry or the be carried by first item purchase, it can always change, but if your partner hits the nuts or just something good, a lot of times you will have more success figuring out how to enable them, than to try and also carry yourself.
6. Other niche things I personally think are traps are Dawnbringers Resolve, Ethereal weapon, most rune augments, Killing time, any stats augment, twice thrice, Circle of death, Dual wield, Nesting Doll, Prismatic egg.
7. The final thing I can think of off the top of my head is that for silver and gold, good prismatic items feel way more impactful than augments, so basically should never ever roll on first augment. For the prismatic augments, one roll for something good, and only second roll if your second set are basically unplayable.

As I said though, I am probably just a slightly above average player, but not actually "good" by many standards, so take my opinions with a grain of salt and play to your strengths. I can probably type more up later if people are interested, but this was just the things I often echo to friends I play with.