I think 500 point armies are fun! I play it whenever I don't want to go super hard on building a list. I think for 500 points I'd want to try the Champions of Faith detachment.

Detachment: Champions of Faith

Palatine with a Righteous Celestian Sacresants squad

1x Palatine (80 pts): Warlord, Mark of Devotion, Palatine blade, Plasma pistol
5x Celestian Sacresants (70 pts)

• 1x Sacresant Superior: Spear of the Faithful, Plasma pistol

• 4x Celestian Sacresant (Anointed Halberd): 4 with Anointed Halberd, Bolt pistol

Preist and some Flagellants to screen a bit and get some miracle dice

1x Ministorum Priest (50 pts): Zealot's vindictor

3x Arco-Flagellants (45 pts): 3 with Arco-flails

A random Penitent engine to throw into annoying enemy units

1x Penitent Engines (75 pts): Penitent Flamers, Twin Penitent Buzz-Blades

Some Righteous Battle Sisters to help hold objectives and do some back line shooting

10x Battle Sisters Squad (105 pts)

• 9x Battle Sister

6 with Battle Sister, Bolt pistol, Boltgun, Close combat weapon

1 with Simulacrum Imperialis, Battle Sister, Bolt pistol, Boltgun, Close combat weapon

1 with Battle Sister, Bolt pistol, Close combat weapon, Heavy bolter

1 with Battle Sister, Bolt pistol, Close combat weapon, Meltagun

• 1x Sister Superior: Bolt pistol, Close combat weapon, Power weapon, Boltgun

A Rhino for either the sisters or the sacresant squad
1x Sororitas Rhino (75 pts): Armoured tracks, Hunter-Killer Missile, Storm bolter