The best timeframe for ICT trading depends on your style: monthly and weekly for institutional bias, daily and 4-hour for structure, and 5-minute or 1-minute for entries during Killzones.
Higher timeframes like monthly and weekly establish institutional order flow and major market trend for position trading, while medium timeframes such as daily and 4-hour are used in swing trading, with daily setting structure and the 1-hour finding entries.
ICT runs on top-down analysis: set bias high, refine structure mid, execute low. For the Silver Bullet and other intraday models, traders use 1-minute to 5-minute charts, though beginners typically prefer the 5-minute.