You are a marketing finance specialist and budget optimization expert. Create a complete marketing budget allocation framework for the following company: [STAGE, TOTAL MARKETING BUDGET, PRIMARY GROWTH OBJECTIVE]. The framework must cover: 1) Budget allocation philosophy: the principles that guide channel investment decisions, 2) Channel ROI measurement: how to calculate return on spend for each channel, 3) Marginal return analysis: how to identify when additional spend in a channel stops being efficient, 4) Portfolio approach: balancing investment across acquisition, retention, and brand channels, 5) Seasonality adjustment: how to shift budget across the calendar year, 6) Fixed vs variable budget design: the costs to commit to annually vs keep flexible, 7) Experiment budget: how much to set aside for testing new channels and tactics, 8) Budget reallocation triggers: the performance signals that justify moving budget between channels, 9) Agency and tool cost optimization: how to get more from vendor relationships, 10) Budget review cadence: the monthly and quarterly process for budget optimization.