New to Slaves to darkness

New to AoS and slaves to darkness: Need advice

I am new to warhammer and am participating in a local gaming store's builders league. The premise is every starts with a 500 point army and every 2 weeks we go up by 250 to a cap of 1500.

What should I run at each level? 500/750/1000/1250/1500

I have a spearhead which allows me to either make 1 unit of warriors with a banner and musician or chosen, with a chaos chariot and a lord with Calvary with both musician and banner with optional upgrade to chosen