Expressing your power level correctly:
1. No anime merchandise for anything that is well known where you live.
2. Don't make a huge deal of it. If someone brings it up, just shrug it off, and mention that it's a hobby. Make sure it doesn't seem like Anime is your only hobby. If it is, get a life.
3. No Moeblob. Period. No one is to know of your secret obsession with young cartoon girls.
In other words,
Black Lagoon and Akagi T-shirts = Okay, if it's not the only thing you wear.
Death Note and FMA T-shirts = No.
One final note. Keep your power level suppressed if you're an undesirable person in any way. No need for the image of anime fans to be further tarnished.