How to create a table under a user

Hello!

I got a problem by creating tables under a user.

I first created a database with oracle universell installer.

I then loged in to it with Toad as SYS and created:

CREATE USER my_user IDENTIFIED BY my_password;

Then I thought that tables etc will be assigned to my_user if I log out SYS and log in as my_user in Toad.

My idea was to do:

CREATE TABLE Countries
(
    id INT NOT NULL,
    name VARCHAR(255) NOT NULL,
    PRIMARY KEY (id)
);

CREATE SEQUENCE Sequence_Countries_id
START WITH 1
INCREMENT BY 1
NOMAXVALUE;

CREATE TRIGGER Trigger_Countries_id
BEFORE INSERT ON Countries
FOR EACH ROW
BEGIN
    SELECT Sequence_Countries_id.NEXTVAL INTO :NEW.ID FROM DUAL;
END;


But when I get to CREATE TRIGGER Trigger_Countries_id I get an error saying, "can not create triggers for object belonging to SYS"

Do you huys see if I'm missing something.

Do need something called tablespace?

Best regards
Fredrik