Definitely not a good idea. Generally, "mainstream" Satanist things that are widely known to the public should be avoided, because you may potentionally attract negative attention with them. What I mean here is some specific tattoos, or wearing jewelry with symbols such as the Inverted Cross, a Goat's head, a Pentagram, Baphomet etc. I would add here the sigils of Demons as well. It's better to be safe when it comes to these things, because you never know at a glance who might have harmful tendencies and feelings towards you. Also, adding your own blood is completely pointless, I would avoid that one too.
A great alternative would be to get "regular" jewelries with a special meaning only you know. On the "Demons" sections on the JoS site you can see the Gods listed for example, most of them have specific colors, crystals, animals and plants listed under their names. If you'd like to own and wear a jewelry that represents your Guardian for example you can choose one of their symbols, and search for a jewelry with it. Generally, necklaces with animal and plant symbols are pretty popular, same goes for jewelries made out of crystals. Many people like to wear them, so if you do the same you won't be seen as suspicious and it won't draw unwanted attention to you. No one thinks of Satanism when seeing someone wearing a cat, or a wolf necklace, after all. So this is a pretty safe way of going around it, and you'II still have a special and personal meaning behind it that only you know.
