Answered for language learning in general. No specific language was set for this question, so the findings are drawn from general second-language research rather than one language’s literature.
There's no single "most efficient" method proven best across the board, but the sources point to a consistent theme: speaking ability improves fastest through structured, repeated practice that combines real communicative use of the language with feedback on fluency and pronunciation, rather than passive study alone. Techniques with the clearest supporting evidence in these sources are audio-lingual style repetition drills, communicative/task-based practice (including games and chatbots), and training that targets specific speech-fluency components (speed, pausing, pronunciation) rather than vocabulary or grammar alone.
A classroom study of 30 students learning Arabic found that heavier use of the audio-lingual method (repetition and pattern drills modeled on native-like audio input) was statistically linked to better speaking skill scores, with students who used the method more scoring higher on speaking tests.9
In plain terms
In studies of second-language speakers, native listeners' judgments of how fluent and understandable someone sounded were most strongly tied to measurable factors like speaking speed, how often and how long a speaker paused, sentence complexity, and pronunciation — not to vocabulary knowledge or minor grammar mistakes.4,6
Example
A study of 40 French learners found that the specific speaking task given (not just overall proficiency) affected fluency measures like speaking rate and pause length, and that learners' own sense of a task being 'difficult' was driven mainly by trouble finding the right words and trouble speaking fluently.6
Example
A study of non-native English speakers found that having intelligible pronunciation was necessary but not sufficient on its own for effective speaking — successful communication also depended on a combination of other pronunciation features interacting together, and there wasn't one single 'magic' feature that made speech clear.5
Practicing speaking through communicative, interactive activities — such as structured conversation games (board games) or AI chatbots that simulate natural dialogue — has been reported to improve speaking competency, increase motivation to speak, and boost learners' confidence and interaction.7,8
Example
In an intervention study with minimally verbal children, those who started with lower language ability showed more improvement from a communication-focused intervention than those who started stronger, though overall gains from the interventions studied were not consistently maintained over time.3
In plain terms
Based on these sources, the most defensible approach to building speaking efficiently combines three elements: (1) repetition-based drilling of model sentences/sounds (audio-lingual style) to build automatic, correct pronunciation and structure; (2) genuine communicative practice — conversation, structured games, or chatbot dialogue — that forces you to retrieve words and respond in real time under mild pressure, since this is what actually builds fluency (speed, fewer pauses) rather than passive listening or grammar study alone; and (3) targeted feedback on the specific fluency and pronunciation features that make you hard to understand, rather than assuming more vocabulary alone will fix intelligibility. Choosing speaking tasks or topics that are appropriately challenging (not so hard that word-finding difficulty overwhelms you) will also help fluency develop faster, since perceived task difficulty is closely tied to how much your speech slows down and breaks up.