There's an entire budget sub-forum. To be honest, building budget is more mentality than anything. Almost any general can be built decently on a budget.
Budget to me says 'slow my clock down by 2-5 turns, and make any infinite combos require 1 or 2 more cards.'
You can pull off any deck, it just wont be as finely tuned.
Perhaps you should ask how to make a deck for a certain general in a budget manner rather than say whats the best budget deck i can build? Especially since thats sorta an open ended question. Do you mean best price thats still competative? or do you mean best competative on a relatively budget price?
There are budget builds in my meta that perform very well in my meta. They typical suck 1v1 but if you are creative and look for budget cards that hose powerful non-budget cards, you can wield a lot of political power. Cards like Torpor Orb, for example, cost next to nothing yet hose so many powerful cards. It is perfectly viable to play cards like that if you don't plan on spending the dough on the cards that they hose.
I ended up taking it apart for winning too consistently, despite the fact that my meta is fairly competitive (people don't run original duals, but they do run swords, elesh norns, and prime times).
Ezuri is probably the main reason I started running various edict effects in my deck. He's a pretty good bet if your opponents started playing after wraths with non-regenerate clauses rotated out of standard, since most newer players just just DoJ and the like.
He is also extremely well-costed for how much utility you have on him. Probably easily one of the top green legendaries.