What is the cheapest light you can use to yield great bud

Buy a used low bay shop fixture off craigslist. There is a thread here on converting them. It's easy. I bought 2 400 watt MH with bulbs for $20 each. They are everywhere on craigslist - used.

https://www.rollitup.org/do-yourself/164853-how-use-industrial-low-bay.html