Taking it you mean the BB, not the chainset, for budget, when I was looking for a ultra budget build last year, I chose a Neco branded square taper BB, which was about half the price of a Shimano UN54/55, so far it's done a over 1200km (will hit 1300km later today) with no issues.
Like this on ebay
https://www.ebay.com/itm/Bottom-Brac...AAAOSwMfhaZsNK