Hi

I think if you want to put in one tablespace alter tablespace´s parameter

minimum extent 128K

this will esure all extents are 128K thus avoiding fragmentation, the deallocated extents will be reused

or

have different inital extents but multiples of smallest extent size and coalesce every once a while, once the extent issue is done just adjust pctfree and pctused parameters for respective table with high inserts/updates/deletes.