What should I do if I got scammed?

Check steamrep, not their steam profile.

Wut? Why you gived MP3 gift as first?

Are you guys thinking sometimes?

Damn, yeah whoever's giving keys should always go first in a trade

I waited for KoA a year to get it on a discount and now it was on amazon D; And i WANTED it so much

General rule is to do several steps

Check rep (if you are new do not trade anyone with less than 10 reps) , check steam account (if private just avoid), check for VAC bans, age (5+ years is solid), game value (1k value minimum), time played (at least 15 hours in 2 weeks) ,then check number of games if at least 100 then will may be okay (recommend at least 200 games), but ideally the trader would have 500-1k games to keep up their reps, make sure the accounts are correct, check if their inventory is private, check which region they are from, and if all else fails report them and wait for bans (sa long as you have picture proof)

Amigo, lo enviará en mi isla, yo me encargo de ella, no podía ser mejor salud!

wtf is KoA? :D

Trading game copies for keys are always 50-50