New guard player I need help expanding my army

I have the combat patrol with

2 cadian shock troopers (one with flamer and melta and the other with flamer and plasma)

1 cadian command squad (with grenade launcher)

1 field ordinance battery (bombast cannons)

1 armored sentinel (with autocannon chainsaw and hunter killer)

I am wanting to get too 1,000 points without breaking the bank but still being viable for casual/lightly competitive play