You would want your table to fit into one large extent.
However, table size may be unpredictable and if you are using locally managed tablespaces (Oracle 8i and above), you need not worry much about fragmentation.
create several tablespaces, probbaly 5, each tablespace suits for each size of segments
use minimum extent clause always, number of extents doesnt really affect perfomance in reading but when allocating it will, dictionary tables would have migrated, chained rows and high ST enqueue contention
in Oracle 8i use
LMT with uniform size extents, create several as above although number of extents doesnt affect perfomance in LMT