Good size for redo logs is 4-10M.
LOG_BUFFER should be at most 1M in 8i. There are several reasons for that. You cannot have better performance if you increase LOG_BUFFER from 1M to 4M. (I assume grjohnson meant LOG_BUFFER not REDO_BUFFER).
2 redo log groups is the minimum, 3 is better, some DBA preffer to have 4 or 5.