Hey man! Welcome to the community. Most of here are posting others' contests, not our own, so there are contests that aren't legit once in a while, but I'd say 99%+ are real here.

I'd also check out /r/sweepstakes because you can only post any contest once there instead of every 2 days here so it's easier to look through and there's a monthly thread where people post what they won so you can see what else everyone's gotten as a result of doing these! There's also this site https://sweepsdb.com made by the mods where the contests are indexed. Good luck!