This is clearly not enough if you need decent security. Today's standards, in symmetric encryption, are the AES and Blowfish algorithms, which you can lookup on google, and in the asymmetric encryption field, the standards are RSA and possibly ECC (Elliptic Curve Cryptography).
Of course, what I said holds if you need maximum security for critical stuff ... if you just want to protect your information from the guy next door, just use your cipher, it should be enough.
The less plaintext you encrypt, the less information the adversary has. However, if it is too small, it can also be predicted. You must choose the most appropriate block size for your uses.