Long or short encryptions? Is it generally considered desirable - or not? - to use an algorithm which encrypts a single byte into a byte array of length around 5 or 10?  Greater length allows me to add additional layers of obfuscation, but I don't know whether this is considered the sign of a naive amateur (which I am).
There is no security improvement for using an algorithm with ciphertext expansion. In fact, it's really only an unavoidable side-effect of certain public key operations. It's not something that's desired.
Anyway, time for the obligatory don't roll your own. No matter how secure you think it is, it isn't. If you want to learn about cipher design, read about existing ciphers, like this one.