A tight budget doesn't mean fewer experiments. It means every experiment has to earn its slot.
The allocation comes first. Under pressure for near-term results, I put 70% to 80% of the budget into channels with proven past performance and reserve 10% to 20% for experiments and long-term brand building. The experiment budget is small on purpose. The discipline is in what you point it at.
I score candidates with one of three frameworks, depending on the decision in front of me.
BRASS (Blink, Relevance, Availability, Scalability, Score), from Growth Tribe, when the question is which channel to try at all. The first four factors score 1 to 5 and multiply out, so one weak factor drags the whole idea down. Availability is the one that saves small businesses: a channel you can't staff this month isn't an option; it's a wish.
PIE (Potential, Importance, Ease), from Chris Goward at WiderFunnel, when the channel already works and the question is which page or asset to fix. It weights traffic, so you stop optimizing pages nobody visits.
ICE (Impact, Confidence, Ease), popularized by Sean Ellis, for the weekly small stuff. It's the most subjective of the three, which is exactly why it fits a team running ten cheap tests instead of one expensive one.
The simple rule underneath all three: spend the smallest amount that can kill the idea. If the result won't change what you do on Monday, it isn't a test; it's content. A test that can only produce a vanity metric isn't a test either.
That rule is what settled a tool everyone swore would bring thousands of followers. I paid the $30 and ran it for a month. Lots of content, zero engagement. End of debate. The payoff wasn't followers; it was the year of spend and arguing we never did.
I might be wrong about which of the three fits your business. Not about scoring before spending.
Stop asking what a test costs. Ask what a wrong answer costs.