Chastity is a complex topic. If you plan to go into chastity I recommend a custom fitted metal device. Be patient as it may take a few adjustments -- I also recommend an oval base ring.

I've been in and out of long-term chastity for over 6 years. Once you have a properly fitted cage, I recommend getting a key holder. There are key holder programs like Chastikey if you don't know anyone to hold your key. I recommend having a pro Dom like Mistress Ayn holding your key. If you're going to play with Chastity for a few days it can be a game -- if you're serious then get a Key Holder if you can. It's always good to set parameters with someone you trust.