If the goal is 500 watts of light, then all you need is 11 sol strips for a total of around $220. Then add a few Meanwell LDD drivers like @ReikoX suggested above - which are very cheap - like under $5 ea. I havent done the math on the drivers required but it would be maybe another $50 at most. Add in a few bucks for mounts and wire and you’re done.
Should be able to do all that for the $400 budget easily.
Of course, that does NOT include the solar cells, batteries, battery charger, etc etc. That part will cost far more than the LED’s or any other kind of lights. Rough guess = $1000 Plus or minus.