What is a good turntable preamp under $500?

The Schiit Mani2 phono preamp- Fremer gave it a very positive review:

https://www.analogplanet.com/content/schiits-mani-2-mmmc-phono-preamp-goes-head-budget-phono-preamp-class-0

Schiit makes high value components consistently performing above their price point.   At $150, this looks like a bargain.

Schiit’s website still shows the Mani and not the Mani2, but per Schiit after ordering:  ”To answer your questions, yes you will be receiving the Mani2 since Mani V1 is no longer available since it's been discontinued. ”

If your intention is simply to get the rig up and running, purchase an old Radio Shack Phono Preamp. They are not screechy like the modern units and can be had for low $. Leave it plugged in for a week or so before judging as they are roughly 40+ years old at this point. 

Lounge Audio's LCR MK III.

IFi Zen phono with the optional ipowerx power supply. 

If you want to run a test without risking much, pick something within your budget from Music Direct. It has a 60-day return policy for full refund. Several of the units mentioned here are available there.