To drop all triggers in a schema, simply execute:

begin
for i in (select trigger_name,owner from dba_triggers where trigger_name like '%') LOOP
execute immediate 'DROP TRIGGER '||i.owner||'."'||i.trigger_name||'"';
END LOOP;
END;

To get drop queries for all tables in a schema, simply execute:

select 'drop table '||table_name||' cascade constraints;' from user_tables;

or you can get drop queries for all user objects in a schema by executing:

select 'drop ' || object_type || ' ' || object_name || ';' from user_objects where object_type != 'INDEX'