Oracle Database Discussions

My database does not get too big. The largest I have is roughly 30g. The average database is probably 5-10g. (These are using a single datafile)

At my largest size (30g), is there any advantage to having multiple data files that are ~5g each instead of one large datafile?

If I initially set up my tablespace to only use 1 datafile with a max size of 5g, can I easily add a second data file with another 5g once the capacity of the first file is neared?